UC-NRI 


, 


THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 


PRESENTED  BY 

PROF.  CHARLES  A.  KOFOID  AND 
MRS.  PRUDENCE  W.  KOFOID 


COMPENDIUM 


OP 


HUMAN    HISTOLOGY. 


o 


COMPENDIUM 


OF 


HUMAN      HISTOLOGY, 


BY    C.    MOEEL, 

PROFESSOR   AGREGE   A   LA    FACULTE"T>E   MEDECINE   DE   STRASBOURG. 


bg  Sfotntg-ngfrf 


TRANSLATED  AND  EDITED  BY 

W.    H.   VAN    BUM,    MJX,-< 

OP    GENERAL     AND     DESCRIPTIVE      ANATOMT     IN     THE      UNIVERSITY     OP    NEW     YORK  J 
MEMBER  OP  TIIE  PATHOLOGICAL  SOCIETY  OF  NEW  YORK,  AC.,  AC. 


NEW    YOEK: 
BAILLlfiRE     BROTHERS,     440     BROADWAY. 


LONDON: 
H.      BAILLIEKE, 

219  BEGENT  ST. 


MELBOUENE : 
F.    BAILLIEKE. 


PAEIS: 

J.   B.  BAILLIEEE  ET  FILS, 
ETTB  HAUTEFETJILLE. 

MADEID : 
C.     BAILLT-BAILLIEEE, 

CALLE  DEL  PRINCIPE. 


1861. 


T4)OJ:( 


in 


Entered  according  to  Act  of  Congress  In  the  year  1869,  by 

BAILLIEKE  BROTHERS, 

In  the  Clerk's  Office  of  the  District  Court  of  the  United  States,  for  the  Southern  District  of 

New  York. 


B.    CKAIGILE.V1), 

Printer,  Stereotyper,  and  Electrotypar, 
CTaiton  JJutfiJt'ng, 

81,  83,  and  85  Centre  Street. 


EDITOR'S  PREFACE. 


I  HAVE  prepared  M.  Morel's  Compendium  of  His- 
tology for  the  use  of  the  American  medical  student 
in  consequence  of  the  excellence  and  fidelity  of  its 
plates,  and  the  clear  and  concise  manner  in  which  all 
that  is  positively  known  of  the  science,  up  to  the  pre- 
sent moment,  is  set  forth  in  the  text. 

An  original  work  of  the  same  character  and  simi- 
larly illustrated  would  involve  a  much  greater 
expense,  even  if  the  same  degree  of  merit  could  have 
been  attained. 

Histology,  at  the  present  day,  is  the  progressive 
department  of  anatomical  science,  and  its  rapidly 
accumulating  facts  form  the  basis  of  modern  physi- 
ology and  pathology.  Still  in  its  youth,  it  is  advanc- 
ing steadily  from  year  to  year,  and  to  keep  pace  with 
its  progress,  we  must  draw  constantly  upon  all  reli- 
able sources  of  information.  In  our  young  and  busy 
country  the  laborers  are  as  yet  too  few,  and  too  much, 
of  necessity,  employed  in  the  active  and  practical 
duties  of  the  medical  profession,  to  institute  original 


vi  EDITOR'S  PEEFAOE. 

and  systematic  researches  in  minute  anatomy  to  any 
great  extent,  and  hence  we  are  mainly  indebted  for 
our  knowledge  of  it  to  our  brethren  of  the  old  world. 
To  solicit  the  attention  of  the  student  to  the  sub- 
ject of  general  anatomy,  and  to  furnish  him  with  an 
attractive  text-book  in  a  less  elaborate  form  than  the 
excellent  works  of  Todd  and  Bowman,  the  Cyclo- 
paedia of  Anatomy,  &c.,  &c.,  is  the  object  with  which 
I  have  prepared  the  present  volume  for  the  press. 
I  trust  it  may  serve  the  purpose  of  an  introduction  to 
the  more  extensive  works  on  the  subject,  and  also  to 
the  numerous  and  faithful  laborers  in  this  department 
of  science  in  Europe,  and  especially  in  Germany, 
where  it  is  most  successfully  cultivated. 

YORK,  October,  1860. 


CONTENTS 


PAGE 

INTRODUCTION,     "  *V     .,      . .  ^p&.L     .     »£.?/jaV'i."L  .w.*:rr*,';    9 


CHAPTER  I. 

CELLS  AND  EPITHELIAL  MEMBRANES,     .        .    ru^     .        .      11 

CHAPTER  H. 

FIBRES;   CONNECTING  TISSUE, 17 

CHAPTER  IH. 

CARTILAGE — BONE — TEETH, 26 

CHAPTER  IV. 

MUSCULAR  TISSUE,       •*        •••,- :v/«        .-       .        .  ,  .  -v       .      45 

CHAPTER  V. 

ELEMENTS  OF  NERVOUS  TISSUE,    .        ."  '    .        .        .        .58 


viii  CONTENTS. 


CHAPTER  VI. 

PAGE 

VESSELS.  —  ARTERIES.  —  VEINS.  —  CAPILLARIES,    AND    LYM- 
PHATICS,        71 


CHAPTER  VII. 

GLANDS. 84 

Of  '*  p-    V*   '";<"  T^  <lVr  f"\  *"  "\ 

CHAPTER  VHI. 
SKIN  AND  ITS  APPENDAGES, 145 

CHAPTER  IX. 

INTESTINAL  Mucous  MEMBRANE,   ....     . '^)\f ^:    155 

CHAPTER  X. 

ORGANS  OF  SENSE,         .       ^itii^uJ     .        .     111?'^!.  <^VL     .     170 

EXPLANATION  OP  THE  PLATES,       .     1]        .        .        .        .185 


COMPENDIUM 


OP 


HUMAN    HISTOLOGY. 


INTRODUCTION. 

THE  science  of  Histology  has  for  its  object  the  study 
of  the  organic  elements  of  the  human  body,  in  refer- 
ence to  their  forms,  the  various  changes  which  they 
undergo,  and  the  part  which  they  perform  in  the  con- 
struction of  its  several  tissues  and  organs. 

In  the  present  state  of  the  science  all  of  the  simple 
elements  of  which  the  body  is  composed  may  be  re- 
duced to  one  of  the  following  typical  forms,  viz : 
1st,  structureless  material ;  2d,  cells ;  3d,  fibres ;  4th, 
crystalline  substance. 

Structureless  material,  or  amorphous  substance, 
exists  either  as  a  liquid  or  solid  ;  in  the  former  con- 
dition it  is  of  constant  occurrence,  in  the  latter  it  con- 
stitutes the  basis  or  fundamental  substance  of  several 
of  the  tissues,  e.g.  bone,  cartilage,  etc. 

The  cell,  in  the  largest  acceptation  of  the  term,  is  a 
vesicle,  varying  greatly  in  shape,  as  well  as  in  size,  and 
consisting  essentially  of  an  envelope,  and  contained 
material  of  diverse  appearance  and  nature. 

1 


10  INTRODUCTION. 

The  fibre,  also  variable  in  size,  is  either  homoge- 
neous throughout  (connective  fibre),  or  it  takes  the 
form  of  a  tube,  the  walls  of  which  are  readily  distin- 
guishable from  its  contents  (muscular  fibre,  nerve 
fibre,  etc.). 

In  the  normal  state  of  the  human  body  crystalline 
substance  has,  up  to  the  present  time,  been  found  only 
in  the  internal  ear,  where  it  constitutes  the  otoliths, 
and  in  the  encephalon ;  it  is  not  positively  deter- 
mined that  the  concretions,  composed  of  concentric 
layers,  which  are  found  in  the  pineal  gland,  are  crys- 
talline in  their  nature. 


CHAPTER    I. 

Cells  and  Epithelial  Membranes. 

SECT.  I.  The  simple  cell  is  the  organ  which  above 
all  others  is  especially  endowed  with  vital  power,  it 
is  the  formative  element,  in  fact,  of  all  the  simple 
tissues,  and  is  therefore,  of  necessity,  our  first  object 
of  study. 

In  every  perfect  cell  we  recognise  the  following 
parts :  (1)  A  containing  membrane,  transparent,  struc- 
tureless, and  exceedingly  thin  and  delicate — the  cell- 
wall  ^  within  this  envelope  (2)  a  liquid  substance, 
generally  transparent  and  granular,  surrounding  an- 
other vesicle,  which  usually  presents  a  more  strongly 
marked  outline  and  thicker  walls  than  those  of  the 
cell,  called  the  nucleus,  or  cyto  blast ;  and  finally,  (3) 
in  the  midst  of  the  granular  contents  of  this  latter, 
we  can  detect,  ordinarily,  a  granular  body  larger  than 
the  rest,  known  as  the  nudeolus.  (PI.  I.  fig.  II.  1,  2, 
3.  PL  II.  fig.  VI,  VII.  PI.  XIII,  fig.  I). 

Whenever  these  constituent  parts  cannot  be  recog- 
nised in  a  cell,  it  is  to  be  inferred  that  it  has  already 
undergone  transformation  from  its  original  condition, 
as  we  find  to  be  the  case,  for  example,  in  blood  glo- 
bules (PI.  I.  fig.  I.  1),  and  fat  cells  (PL  I.  fig.  V.) 

The  contents  of  the  cell,  exclusive  of  its  nucleus 
and  nucleolus,  have  been  described  as  ordinarily 
liquid,  transparent,  and  finely  granular.  Sometimes, 
however,  these  transparent  granules  are  replaced, 


of 


12  CELLS    AND   EPITHELIAL   MEMBRANES. 

entirely  or  in  part,  by  minute  masses,  or  grains,  of  an 
opaque  and  very  dark  colored  substance  (pigment), 
such  as  are  to  be  seen,  for  example,  in  the  pigment 
cells  of  the  choroid,  of  the  iris,  and  in  many  iierve- 
cells.  (PL  II.  fig.  I,  II.,  PI.  XIII.  fig.  I.  6.)  There 
are  cells,  also,  which  in  their  normal  condition  con- 
tain numerous  minute  spherical  globules  with  a  clearly 
defined,  dark  outline,  and  possessing  a  very  highly 
refractive  power ;  these  little  pearl-like  bodies  are 
nothing  more  than  free  fat,  and  are  known  as  oil- 
globules.  Hepatic  cells  always  contain  a  variable 
quantity  of  them,  and  globules  of  colostrum  are  filled 
with  them.  (PL  I.  fig.  Ill,  PL  XVIII.  fig.  VI.  2.) 
The  same  is  true  of  the  cells  of  sebaceous  glands. 

The  presence  of  oil  globules  in  a  cell  which  nor- 
mally contains  none,  is  evidence  of  its  approaching 
degeneration,  and  indicates  arrest,  or,  at  least,  tem- 
porary perversion  of  its  physiological  development. 
This  is  to  be  seen  in  the  pulmonary  epithelial  cells 
while  tubercular  deposit  is  taking  place  ;  it  is  also  the 
anatomical  lesion  of  the  cells  of  renal  epithelium  in 
Bright's  disease.  Finally,  crystals  are  sometimes 
formed  in  the  cells  of  adipose  tissue.  (PL  II.  fig.  IV.) 

When  cells,  and  especially  young  cells,  are  sub- 
jected to  the  action  of  acetic  acid  under  the  micro- 
scope, both  the  cell  wall  and  its  contents  very  soon 
begin  to  grow  pale,  but  their  nuclei  become  more  dis- 
tinct; after  a  time  the  cell  wall  melts  down  and  dis- 
appears, but  the  nucleus  retains  its  natural  appear- 
ance. If,  in  place  of  acetic  acid,  caustic  potash 
be  applied  in  the  same  manner,  even  though  largely 
diluted,  the  cell  begins  at  once  to  swell  up,  grows 


CELLS   AND    EPITHELIAL   MEMBRANES.  13 

pale,  and  finally  disintegrates  entirely ;  its  elementary 
molecules,  or  granules,  alone  seem  to  possess  the  pro- 
perty of  resisting  the  action  of  this  chemical  agent. 

Although  varying  greatly  in  shape,  all  cells  may  be  Different 
arranged  under  one  of  the  following  distinctive  types : 
1st,  spherical  cells  ;  2d,  many-sided  cells  ;  3d,  scales ; 
4th,  conical  or  cylindrical  cells ;  5th,  ciliated  cells ; 
6th,  fusiform  cells ;  7th,  branching,  or  star-shaped 
cells. 

To  the  first  class  belong  the  embryonic  ovule,  and  Giobuiaror 

w  spherical  cells. 

the  cells  developed  directly  from  it ;  newly  formed 
cells  in  the  adult,  and,  in  general,  all  cells  which  float 
in  a  liquid  medium. 

The  second  class  includes  the  deeper  seated  cells  of  Polygonal  or 

many-sided  cells 

many  of  the  epithelial  membranes ;    the  epithelial  and  8cale8- 
cells  of  glands  composed  of  clustered  follicles,  and  of 
some  glands  of  tubular  structure.     Cells  in  the  form 
of  scales  are  found  only  in  the  superficial  layer  of  the 
epidermis  and  epithelium  of  the  tongue. 

The  deep  layer  of  almost  all  the  epithelial  mem-  comcai  ceiis. 
branes  which  present  a  stratified  arrangement  of  their 
cells,  the  epithelium  of  the  intestinal  canal,  and  of  its 
tubular  follicles,  and  that  of  a  large  proportion  of  the 
excretory  ducts  of  glands,  are  made  up  of  conical  or 
cylindrical  cells,  (PL  XXIII.  fig.  II.  3,  PL  XXVI.  fig. 
VI.  fig.  XL) 

The  free  surfaces  of  the  epithelial  cells  lining  the  cmated  ceiis. 
walls  of  the  air  passages,  uterus,  fallopian  tubes,  etc., 
are  furnished  with  a  great  number  of  minute  hair-like 
projections  (called  cilia  from  their  resemblance  in 
shape  to  an  eye-lash)  .which  possess  during  life  a 
peculiar  vibratile  motion,  always  in  the  same  direc- 


14  CELLS    AND    EPITHELIAL    MEMBRANES. 

tion ;  these  constitute  the  fifth  class,  and  are  known 
as  ciliated  cells.     (PL  I.  'fig.  VII.) 

Fusiform  ce'.is.  Fusiform  cells  are  found  principally  in  tissues  of 
recent  origin  which  are  undergoing  fibrous  transfor- 
mation ;  cicatrices  are  formed  by  this  class  of  cells, 
and  some  tumors  are  composed  almost  entirely  of 
them.  (PI.  IV.  fig.  IV.) 

^he  ^as^  c^ass  comPrises  those  cells  in  which  the 
cell  wall  is  developed  into  tubular  or  filiform  prolon- 
gations or  branches.  Examples  :  Most  nerve  cells  of 
the  nervous  centres  and  ganglia ;  the  cells  of  the  ex- 
ternal surface  of  the  choroid ;  bone  cells,  plasmatic 
cells,  etc.  (PL  XIII.  fig.  I.,  fig.  II.,  PL  V.  fig.  IV.,  PL 
III.  fig.  IV.) 

Every  cell  must  derive  its  origin  from  another  pre- 
viously existing  cell.  In  the  present  state  of  science 
but  two  modes  are  known  in  which  cell  generation  is 
accomplished  in  human  histology:  endogenous  gene- 
ration, and  multiplication  by  cleavage. 

In  endogenous  generation  the  process  is  not  always 
exactly  the  same  ;  sometimes  the  nucleus  of  the  pri- 
mitive cell  developes  itself  into  two  secondary  nuclei, 
each  of  which  on  the  disappearance  of  their  common 
envelope,  surrounds  itself  by  a  portion  of  the  granular 
contents  of  the  cell,  and  a  new  cell  wall  making  its 
appearance  on  its  surface,  (Kolliker),  the  infant  cell  is 
thus  completed;  (segmentation  of  the  yelk).  In 
other  cases  the  young  nuclei,  instead  of  making  their 
appearance  first  in  the  interior  of  the  nucleus  of  the 
primitive  cell,  develope  themselves  directly  from  the 
granular  contents,  and  then  grow  into  perfect  cells  in 
the  mode  already  described ;  e.g.  cells  of  foetal  mar- 
row. (PL  VI.  fig.  IV.) 


CELLS    AND    EPITHELIAL    MEMBRANES.  15 

The  mechanism  of  the  process  of  generation  by 
cleavage  is  as  follows : 

The  primitive  nucleus  developes  itself  into  two 
secondary  nuclei,  or,  two  nuclei  may  exist,  from*  its 
formation,  in  the  primitive  cell ;  then  the  cell  wall 
contracts  like  an  hour-glass  enclosing  a  nucleus  in 
either  end,  and  finally  a  separation  takes  place  at  the 
contracted  portion,  the  result  of  this  metamorphosis 
being  two  perfect  new  cells ;  (Ex.  cells  of  cartilage, 
cells  of  epithelium  of  intestine). 

SECT.  II.  EPITHELIAL  MEMBRANES. — The  term  Epi- 
thelium is  applied  to  a  class  of  membranes  formed 
exclusively  of  cells,  and  ordinarily  very  thin  and  deli- 
cate. They  invest  all  of  the  free  surfaces  which  the 
body  presents ;  thus  the  external  integument  is  every- 
where clothed  with  an  expansion  of  epithelium,  or 
epidermis,  and  the  same  is  true  of  all  mucous,  serous, 
and  synovial  membranes,  and  of  the  membranes  lining 
the  cavities  of  the  secreting  glands,  blood-vessels,  and 
lymphatics.  In  view  of  the  different  shapes  of  the 
cells  of  which  epithelial  membranes  are  composed, 
they  are  divided  into  three  groups,  or  classes:  1st, 
polygonal  or  scaly  epithelium  ;  2d,  cylindrical  or  co- 
nical ;  and  3d,  ciliated  epithelium. 

Epithelial  cells  are  in  some  instances  spread  out  so 
as  to  form  a  simple  lamina ;  in  others  they  are  found 
in  several  layers,  one  superimposed  upon  another. 
The  first  mode  of  arrangement  constitutes  simple  epi- 
thelium /  the  second  is  known  as  stratified  epithelium. 

Heretofore  the  study  of  cells  and  epithelial  mem- 
branes has  been  too  much  neglected ;  and  yet  there 
are,  in  truth,  no  histological  elements  of  more  import- 


16  CELLS    AND    EPITHELIAL   MEMBKANES. 

ance — from  whatever  point  of  view  they  may  be 
regarded.  For  is  not  the  simple  cell  the  constituent 
or  formative  element  of  all  the  normal  tissues,  as  well 
as  of  those  which  result  from  diseased  action  ?  And 
of  the  latter,  those  over  which  our  remedies  exert  the 
least  power  are  composed  almost  exclusively  of  cells. 
Still  farther :  those  organs  of  the  body  which  hold 
the  highest  rank  in  view  of  the  importance  of  their 
functions,  which,  in  other  words,  possess  the  greatest 
amount  of  vital  force,  consist  in  the  greatest  propor- 
tion of  cells;  whilst  the  elementary  fibre,  and  the 
organs  mainly  formed  by  it,  perform  functions  which 
are  simply  mechanical. 


CHAPTER  II. 
Fibres ;  Connecting   Tissue. 

4 

THE  essential  elements  of  connecting  tissue*  are 
fibres,  and  cells.  Its  fibres  are  of  two  kinds,  viz: 
connective  fibres  properly  RO  called,  and  elastic  fibres. 
Its  cells  are  diminutive  in  size,  generally  branched, 
but  sometimes  fusiform,  and  have  received  from  Vir- 
chowf  the  name  vi plasmatic  cells. 

The  elementary  connective  fibre  is  so  exceedingly  fibSLectIve 
delicate  in  its  proportions  that  it  is  impossible  to 
measure  its  dimensions.  Generally  collected  in  fas- 
ciculi or  bundles,  they  run  parallel  with  each  other, 
their  outlines  showing  a  slightly  wavy  or  undulating 
disposition.  In  certain  organs,  tendons,  for  example, 
all  the  fasciculi  of  connective  fibres  are  parallel 
to  each  other.  (PL  III.  fig.  I. ;  fig.  III.  1 ,  PL  IV.  fig. 
I.  1;  fig.  II.  1.)  In  the  aponeuroses,  the  skin,  the 
mucous,  serous,  and  synovial  membranes,  they  interlace 
so  as  to  form  a  tissue  or  web,  with  meshes  of  varying 
size.  (PL  II.  fig.  IX.)  These  facts  are  readily  de- 
monstrated by  examining  a  small  fragment  or  slice 
from  the  surface  of  an  aponeurosis  or  tendon,,  care 

*  The  term  connecting  tissue  is  employed  throughout  the  present  work 
to  designate  that  tissue  heretofore  generally  known  as  cellular,  areolar 
or  filamentous  tissue. — (Ed.) 

t  Rodolphe  Virchow,  Professor  of  Pathological  Anatomy  in  the  Uni- 
versity of  Berlin. — (Ed.) 


18  PTBRKH;  CONNECTING  TISSUE. 

being  taken  to  cut  in  the  direction  of  the  fibres  of  the 
latter. 

Elastic  fibres  are  of  larger  size  than  those  just  de- 
scribed ;  the  smallest,  measure  T-ro  o-th  of  aline  in  breadth, 
but  they  may  reach  ^th  of  a  line  (elastic  coat  of  veins, 
PI.  XVI.  fig.  IV.  1).  Their  outlines  are  clearly 
marked  by  one,  and  more  frequently  by  two  black 
lines,  between  which  is  to  be  seen  an  entirely  unor- 
ganized and  transparent  substance.  They  give  off 
branches,  also,  in  every  direction,  and  these  divisions 
uniting  again  with  each  other,  form  a  network  of 
variable  closeness.  Ordinarily,  the  principal  branches 
of  a  fasciculus  of  elastic  fibres  run  parallel  with  each 
other,  as  in  the  yellow  elastic  ligaments  of  the  spine, 
(PL  III.  fig.  V.  1) ;  but  the  secondary  branches  which 
they  give  off  present  very  well  marked  undulations, 
and  most  frequently  curl  upon  themselves.  (PL  III. 
fig.  V.  2 ;  PL  XV.  fig.  VI.  1.)  Following  this  de- 
scription it  is  hardly  possible  to  confound  elastic  and 
true  connective  fibres  with  each  other,  but  we  possess 
additional  means  of  bringing  out  their  distinctive 
characteristics,  by  the  use  of  certain  chemical  reagents. 
Thus,  when  we  subject  the  connective  fibre  to  the 
action  of  acetic  acid,  it  becomes  so  pale  as  to  be  unre- 
cognisable, and  finally  dissolves  entirely  in  the  liquid ; 
the  same  result  follows,  and  even  more  rapidly,  on  the 
application  of  diluted  caustic  potash.  These  reagents 
produce  no  alteration  whatever  in  the  appearance  of  the 
elastic  fibres ;  dilute  caustic  potash  is  even  employed  in 
preparing  clean  and  perfect  specimens  of  them.  To  effect 
this,  a  piece  of  yellow  elastic  ligament  is  to  be  boiled 
for  fifteen  or  twenty  minutes  in  water  containing  some 


FIBRES;  CONNECTING  TISSUE.  19 

of  the  alkali.  All  of  the  other  elements  which  enter 
into  the  composition  of  the  ligamentous  tissue  are  dis- 
solved, whilst  the  elastic  fibres  remain  unchanged. 

The  cellular  element  of  connecting  tissue  (the  plas- 
matic  cell)  is  a  reeent  discovery ;  we  are  indebted  to 
Virchow  for  the  first  thorough  exposition  of  its  nature, 
and  especially  of  its  important  pathological  relations.* 

Plasmatic  cells  are  minute  corpuscles,  sometimes  piasmatic  ceiis, 
fusiform,  but  more  frequently  star-shaped,  with  sharp 
outlines,  and  connected  with  each  other  by  means  of 
their  branching  prolongations,  so  as  to  constitute  a 
network  similar  to  that  formed  by  the  cells  of  bone. 
(PL  III.  fig.  II.  1  ;  fig.  III.  2 ;  fig.  IV.  3.) 

In  tendons,  we  find  piasmatic  cells  arranged  in  a 
longitudinal  series,  between  the  fasciculi  of  connective 
fibres.  (PL  III.  fig.  II.  and  III. ;  PL  IV.  fig.  I.)  In 
the  skin  and  mucous  membranes  they  are  distributed  * 

*  It  will  have  been  already  noticed  by  the  reader,  familiar  with  the 
present  attitude  of  Histology  in  Germany,  that  our  author  has  fully 
adopted  the  somewhat  novel  views  of  the  celebrated  Professor  of  Berlin. 
The  assertion  in  the  preceding  chapter,  that  every  cell  must  take  its 
origin  from  a  previously  existing  cell,  is  one  of  the  new  doctrines  of  Vir- 
chow, who  denies  that  cells  ever  make  their  appearance  by  spontaneous 
generation,  according  to  the  generally  received  pathology  of  the  present 
day,  in  an  appropriate  blastema  or  exudation,  and  insists  that  they  a^e 
always  produced  by  endogenous  growth,  or  by  fissure  and  cleavage  of 
preexisting  nuclei  and  cells. 

The  discovery  of  the  so-called  piasmatic  cell,  as  an  element  of  con- 
necting tissue,  was  first  announced  by  Virchow  at  Wurzburg,  where 
he  was  then  professor,  in  1851,  and  these  cells  play  a  most  important 
part  in  the  new  pathological  views  which  have  since  been  so  ably  deve- 
loped in  his  more  recent  and  elaborate  work  on  "  Cellular  Pathology," 
published  at  Berlin  in  1858.  Their  existence  was  at  first  disputed  by 
Henle,  but  admitted  by  Kolliker,  Leydig  of  Wurzburg,  Weber  of  Bonn, 
and  most  other  German  authorities. — (Ed.) 


20  FIBRES;  CONNECTING  TISSUE. 

more  irregularly.  In  studying  the  cells  in  tendon, 
both  longitudinal  and  transverse  sections  must  be 
examined,  in  order  to  see  them  well ;  their  branching 
disposition  can  be  clearly  recognised  only  in  the 
latter.  (PL  III.  fig.  IV.  3.) 

Plasmatic  cells  are  most  advantageously  studied, 
however,  in  the  cornea ;  its  entire  substance,  between 
the  two  layers  of  epithelium  which  invest  its  anterior 
and  posterior  surfaces,  consists  of  an  amorphous  ma- 
terial in  which  we  find  myriads  of  star-shaped  cells 
arranged  in  regular  concentric  lines  running  parallel 
with  its  surfaces.  The  numberless  branches  given 
off  by  the  cells,  on  every  side,  anastomose  in  such  a 
manner  as  to  form  a  very  beautiful  network.  Very 
dilute  acetic  acid  must  be  applied  to  the  section  under 
examination ;  if  the  acid  is  too  strong  the  branches  of 
the  cells  are  rendered  invisible,  and  the  cells  them- 
selves appear  simply  fusiform,  or  spindle-shaped.  (PI. 
II.  fig.  V.) 

In  the  way  of  normal  development,  these  plasmatic 
cells  may  transform  themselves  into  cartilage  cells,  as 
in  some  tendons  in  old  age,  the  inferior  extremity  of 
the  tendo  achillis,  for  example,  and  the  cartilaginous 
enlargement  of  the  peronceus  longus,  where  it  plays 
over  the  cuboid  bone.  This  transformation  is  effected 
by  the  disappearance  of  the  branches  of  the  cell,  and 
the  production  of  an  external  envelope,  which  thickens 
into  cartilage.  (PI.  IV.  fig.  I.  2 ;  fig.  II.  2.) 

They  are  metamorphosed  in  a  like  manner,  in  the 
periosteum,  into  bone  cells,  by  investing  themselves 
with  a  coating  of  earthy  salts ;  it  is  also  through  the 
agency  of  these  cells  that  layers  of  new  bone  are  de- 


FIBKES;    CONNECTING    TISSUE.  21 

posited  by  the  periosteum  in  certain  stages  of  perios- 
titis. Senile  opacity  of  the  cornea  is  likewise  ex- 
plained by  the  appearance  of  oil-globules  in  the  inte- 
rior of  its  plasmatic  cells.  Finally,  the  researches  of 
Virchow  tend  to  prove  that  all,  or  nearly  all,  of  the 
morbid  formations  developed  in  the  meshes  of  the 
connecting  tissue  throughout  the  body,  are  traceable 
to  the  perverted  growth  of  plasmatic  cells. 

Connecting  tissue,  then,  is  made  up  of  the  three  connecting 
elements  just  studied,  mingled  together  in  variable 
proportions,  and,  with  them,  of  vessels  and  nerves, 
also  variable  in  number.     But  it  is  to  be  observed 
that  these  latter  exist  in  connecting  tissue  as  accessory  vessels. 
elements  only.     Thus,  the  numerous  vessels  habitually 
formed  in  certain  layers  of  connecting  tissue,  as  for 
example  in  that  which  underlies  the  mucous  mem- 
brane of  the  intestinal  canal,  or  some  portions  of  the     * 
external  integument,  have  nothing  whatever  to  do 
with  the  nutrition  of  the  connecting  tissue  around 
them ;  they  merely  pass  through  it  to  their  ultimate 
destination,  and  are  proportionate  in  number  to  the 
importance  of  the  function  to  which  they  minister — 
whether  they  furnish  materials  for  important  secre-  * 
tions,  as  in  the  one  case,  or  in  the  other,  as  bearers  of 
caloric,  are  destined  merely  to  keep  up  the  heat  of  a 
part. 

In  the  substance  proper  of  connecting  tissue  the 
phenomena  of  nutrition  are  of  rather  a  low  order. 
The  simple  diffusion  of  the  nutritious  fluid  exuded 
from  an  occasional  blood-vessel  suffices  to  keep  up  the 
vitality  of  the  elements  which  compose  it.  This  is 
confirmed  by  examination  of  the  structure  of  a  tendon, 


22  FIBRES;  CONNECTING  TISSUE. 

or  of  the  cornea.  There  are  few  organs  so  poorly 
supplied  with  blood-vessels  as  the  former ;  and  in  the 
latter  there  are  none  whatever.  It  follows,  then,  that 
the  fluid  from  which  they  derive  their  sustenance 
penetrates  by  imbibition  into  their  substance,  or  that 
Nerves,  it  gets  there  through  a  net-work  of  plasmatic  cells. 
There  are  very  few  nerves  which  properly  belong  to 
connecting  tissue;  it  is  true  that  some  of  its  mem- 
branous expansions  contain  a  large  number,  but  they 
do  not  minister  either  to  the  nutrition,  or  to  the 
general  sensibility,  of  the  tissue  which  surrounds  them. 
The  comparative  study  of  nervous  distribution  in  ten- 
dons, and  in  certain  regions  of  the  skin  confirms  this 
view. 

We  may  conclude  then  that,  for  its  own  use,  con- 
necting tissue  is  but  scantily  supplied  with  blood- 
vessels and  nerves ;  it  bears  to  them  mainly  the  rela- 
tion of  a  mechanical  support. 

Distribution.  Connecting  tissue  is  distributed  very  generally  and 
universally  throughout  the  body,  either  collected  in 
bundles  or  fasciculi  of  fibres,  or  spread  out  in  the  form 
of  a  membranous  expansion.  It  serves  as  the  bond 
of  union  between  the  several  parts  of  an  organ,  and 
it  maintains  entire  organs  in  their  proper  relations  to 
each  other.  Alone,  it  constitutes  tendons,  ligaments, 
aponeuroses,  periosteum,  perichondrium,  the  dura- 
mater,  pia-mater,  and  sclerotica.  As  membrane,  in- 
vested with  epithelium,  it  constitutes  the  serous,  syno- 
vial,  and  mucous  membranes,  as  well  as  the  skin, 
and  the  membranous  expansion  which  forms  the  basis 
of  most  glands. 

The  vitreous  humor  of  the  eye,  and  similar  hyaline 


FIBRES;  CONNECTING  TISSUE.  23 

and  gelatiniform  tissues,  composed  of  an  amorphous 
substance,  throughout  which  a  variable  number  of 
branching  or  plasmatic  cells  are  distributed,  consist, 
probably,  of  connecting  tissue  in  an  embryonic  or 
imperfectly  developed  state. 

The  fibres  of  connecting  tissue  develop  themselves  Development, 
from  cells  of  the  simplest  form,  which  commence  the 
process  by  assuming  an  elongated  shape,  then  join 
each  other — end  to  end,  and  gradually  break  up  into 
fibres  within,  so  (see  fig.  III.  pi.  IV.)  that  each  row  of 
cells  thus  attached  by  their  extremities,  is  developed 
into  a  bundle  of  connective  fibres.  Whilst  the  majority 
of  the  original  cells  are  thus  transforming  themselves 
into  connective  fibres,  others  assume  a  star-shape,  send- 
ing out  branching  processes,  which,  joining  themselves 
to  similar  prolongations  from  neighboring  cells,produce, 
after  the  disappearance  of  their  nuclei,  elastic  fibres. 
The  cells  heretofore  called  u  plasmatic"  are  nothing 
more  than  the  star-shaped  corpuscles  just  described, 
before  taking  on  their  final  transformation  into  elastic 
fibres.  This  is  the  mode  of  development  of  the  fibres 
of  connecting  tissue  most  generally  admitted,  but  we 
have  recently  recognised  two  other  moc[es  in  which 
connective  fibres  are  formed,  which  have  never  been 
described,  and  which  perhaps  are  worthy  of  notice. 
A  fibrous  tumor  of  the  dura-rnater,  of  an  encephaloid 
aspect,  presents,  in  its  softer  portions  a  series  of  oval 
or  fusiform  cells,  arranged,  end  to  end,  in  longitudinal 
rows  (PL  IV.  fig.  IV.  2).  In  the  harder  parts  of  the 
same  tumor,  where  to  the  naked  eye  it  has  a  distinctly 
fibrous  appearance,  its  cells  are  longer  and  more 
thread-like,  their  bodies  have  become  more  atte- 


24  FIBRES;  CONNECTING  TISSUE. 

nuated,  and  their  nuclei,  apparently  from  increasing 
compression,  have  withered  and  mostly  disappeared 
entirely.  Meanwhile  these  elongated  cells,  in  contact 
by  their  extremities,  have  grown  together,  and  thus 
become  transformed  into  a  continuous  fibre.  The 
essential  feature  in  this  process,  and  that  in  which  it 
differs  from  the  usual  mode  of  development,  consists 
in  the  fact  that  there  is  no  tendency  observed  in  the 
cell  contents  to  break  up  into  fibres,  so  that  each  row 
of  cells  is  eventually  fused  into  but  one  solitary  fibre, 
and  not  into  a  bundle  of  fibrillse ;  (PL  IV.  fig.  IV.  3). 

In  the  other  mode  of  development  of  connecting 
tissue,  which  we  had  an  opportunity  of  studying  in  a 
fibrous  tumor  of  the  uterus,  the  formation  of  the  fibre 
seemed  to  be  due  to  the  metamorphosis  of  free  nu- 
clei. At  certain  points  of  the  tumor  an  agglomeration 
of  oval,  or  spherical  nuclei  was  observed,  imbedded  in 
a  soft  amorphous  substance  (blastema).*  The  out- 
lines of  these  nuclei  were  clear  and  well  marked ; 
their  contents  were  composed  of  very  fine  granules, 
in  some  instances  so  grouped  as  to  represent  a  nucle- 
olus.  Very  rarely  an  outline  representing  the  trace 
of  a  cell-wall  could  be  recognised.  They  measured 
about  T iFth  of  a  line  in  diameter.  (PL  IV.  fig.  V). 

At  other  points  these  nuclei  were  seen  more  elon- 
gated in  their  shape,  stretching  themselves,  as  it  were, 
in  the  blastema  in  which  they  were  imbedded,  and 
becoming  connected  together  by  their  extremities  so 
as  to  form  one  fibre  out  of  each  row  of  elongated 

*  This  term,  originally  introduced  by  Schwann,  signifies  a  soft,  solid, 
hyaline  or  amorphous  materials-such  as  that  in  which  cell  growth  usually 
takes  its  origin.— (Ed.) 


FIBRES  ;    CONNECTING   TISSUE.  .  25 

nuclei  (PI.  IV.  figs.  VI.  and  VII.).  During -this 
process  of  development  of  the  nuclei  the  blastema 
underwent  no  change,  and  showed  no  disposition  to 
take  on  a  fibrous  arrangement ;  it  simply  diminished 
in  quantity. 

Finally,  some  observers  have  asserted  that  simple 
amorphous  substance,  presenting  no  trace  of  orga- 
nization, was  capable  of  undergoing  spontaneous 
transformation  into  connecting  tissue.  Thus  far  we 
have  failed  to  recognise  this  mode  of  development, 
and,  moreover,  are  indisposed  to  admit  the  possibility 
of  the  spontaneous  generation  of  a  recognisable  tis- 
sue in  an  entirely  unorganized  and  amorphous  mass 
of  substance. 


CHAPTER   III. 
Cartilage — Bone —  Teeth. 

SECT.  I.  CARTILAGE. — The  tissue  known  as  cartilage 
consists  of  cells  of  characteristic  appearance  imbedded 
in  a  peculiar  material — which  we  shall  designate,  as 
the  fundamental  substance  of  cartilage.     This  latter 
exists  in  two  forms,  the  one  entirely  structureless,  the 
other  distinctly  fibrous;  hence  the  two  varieties  of 
the  tissue :  true  cartilage  and  fibro-cartilage. 
cartilage  ceils.       The  perfectly  formed  cartilage  cell,  such  as  we  find, 
for  example,  in  the  interior  of  an  adult  costal  cartilage, 
is  usually  spherical,  or  many-sided,  and  of  conside- 
rable volume  (sVth — roth  of  a  line),     It  consists  of  an 
external  envelope  with  transparent  granular  contents, 
presenting  no  peculiar  features;  but  the  nucleus  is 
filled  with  large  sized  oil-globules  to  such  an  extent 
that  no  nucleolus  is  distinguishable  (PL  V.  fig.  I). 
Sometimes  even  the  granular  contents  of  the  cell  are 
replaced  by  these  oil-globules  so   completely  as  to 
give  it  the  appearance  of  a  vesicle  filled  by  a  drop  of 
oil.     In  childhood,  and  on  the  surface  of  the  cartilages 
of  the  adult,  the  cells  are  of  smaller  size  and  elongated 
in  shape,  and  contain  very  little  free  fat,  especially  in 
the  foetus. 

But  the  distinctive  characteristic  of  the  cartilage 
cell  is  the  existence  of  a  structureless  membrane,  or 
capsule,  which  surrounds  it  completely  on  all  sides, 
and  which  is  continuous  bv  its  external  surface  with 


CARTILAGE. BONE. TEETH.  27 

the  fundamental  substance  of  the  tissue.  Sometimes 
this  capsule  includes  but  one  cell,  and  this  we  see  in 
examining  a  cartilage  near  its  surface  (PL  V.  fig.  II)  ; 
more  frequently,  however,  it  encloses  several,  but 
rarely  more  than  five  or  six  (PL  V.  fig.  I).  > 

The  fundamental  substance  of  true  cartilage  is  a 
hard  and  elastic  material  in  which  no  trace  of  struc- 
ture can  be  detected.  In  old  age,  and  sometimes 
even  in  adult  life,  it  becomes  infiltrated  with  fat,  and 
often  presents  minute  cracks — which  appearance  has 
been  mistaken  for  the  spontaneous  generation  of  fibres 
in  a  structureless  material.  But  in  reality  they  are 
no  more  fibres  than  the  granular  striae  of  fibrine — to 
which  they  Bear  an  accurate  resemblance. 

This  fatty  transformation,  or  atrophy,  is  often  found 
in  the  costal  cartilages,  and  is  recognisable  by  the 
naked  eye  in  the  form  of  dead  white  or  reddish  yel- 
low spots. 

Cartilage  is  made  up  exclusively  of  the  elements 
just  described.  In  adult  life  neither  nerves  nor  blood- 
vessels can  be  recognised  in  it.  The  latter,  it  is  true, 
are  occasionally  encountered,  but  only  during  the 
forming  stage  of  the  tissue,  or  where  it  is  undergoing 
transformation  into  bone,  as  we  shall  see  hereafter. 
Thus,  to  sum  up  in  a  word,  true  cartilage  consists  of 
a  structureless  fundamental  substance  or  basis,  studded 
with  minute  cavities,  lined  by  a  membrane,  and  en- 
closing cells. 

Cartilages  are  enveloped  by  a  membrane  called 
perichondrium.  This  membrane  is  formed  by  an 
interlacement  of  connective  fibres  with  delicate  elastic 
fibres,  an  occasional  nervous  fibrilla,  vessels  in  vari- 


CARTILAGE. BONE. TEETH. 


Relations    be- 
tween cartilage 
and  bone. 


Articular  carti- 
lage. 


Distribution. 


able  quantity,  and  plasm atic  cells.  These  latter  exist 
in  greatest  number  in  the  deepest  portions  of  the 
membrane,  and  it  is  to  be  noticed  that  those  in  imme- 
diate contact  with  the  surface  of  the  cartilage  are  not 
distinguishable  in  appearance  from  cartilage  cells 
(PL  V.  fig.  II).  Are  we  not  justified  in  concluding 
from  this  fact  that  the  growth  of  cartilage  is  effected 
by  the  transformation  of  these  plasmatic  cells  of  its 
perichondrium  ? 

Cartilages  are  united  to  bones  by  immediate  con- 
tact or  apposition ;  there  is  no  substance  or  tissue 
interposed  between  them.  Their  opposed  surfaces 
are  rough,  and  their  minute  elevations  and  depressions 
fit  into  each  other  accurately. 

It  was  supposed  for  a  long  time  that  the  free  sur- 
faces of  articular  cartilage  were  invested  with  syno- 
vial  membrane.  Careful  examination  of  the  surface 
of  the  cartilage  demonstrates,  however,  that  within 
the  cavity  of  a  joint  it  is  entirely  naked ;  it  is  not 
even  covered  by  the  epithelial  layer  of  the  synovial 
membrane.  It  is  incorrect  therefore  to  describe 
synovial  membranes  as  shut  sacs,  and  as  lining  the 
whole  interior  surface  of  an  articular  cavity.  A  syno- 
vial membrane  simply  covers  the  internal  surface  of 
-the  capsular  expansion  which  surrounds  the  joint,  or, 
to  be  more  exact,  it  is  nothing  more  than  the  capsule 
of  the  joint  covered  internally  by  a  layer  of  epithe- 
lium. It  is  to  be  understood,  however,  that  those 
ligaments  which  present  a  free  surface  in  the  cavity 
of  a  joint  are  also  invested  by  epithelium. 

Under  the  head  of  true  cartilage  are  included: 
the  cartilaginous  skeleton  of  the  foetus,  the  costal  car- 


CARTILAGE. BONE. TEETH.  29 

tilages,  those  of  the  joints,  the  cartilages  of  the  nose, 
the  thyroid,  cricoid,  and  arytenoid  cartilages,  and 
the  cartilaginous  rings  of  the  trachea  and  bronchial 
tubes. 

Fibro-cartilage  differs  from  true  cartilage  only  in 
the  nature  of  its  fundamental  substance  or  basis, 
which,  instead  of  being  structureless,  is  fibrous.  The 
fibres  of  which  it  consists  are  of  the  elastic  variety,  at 
least  in  most  fibro-cartilages  (PL  V.  fig.  III).  The 
intervertebral  discs  and  the  semi-lunar  cartilages  of 
the  knee-joint  we  have  found  to  be  the  only  excep- 
tions to  this  rule ;  their  fundamental  substance  con- 
sisting almost  entirely  of  connective  fibres. 

The    principal    fibro-cartilages   are   those   of  the  Distribution. 
external  ear  and  Eustachian  tube,  the  epiglottis,  the 
little  cartilaginous  masses  at  the  summits  of  the  ary- 
tenoid cartilages,  the  intervertebral  discs,  and  inter- 
articular  cartilages. 

Cartilage,  like  all  other  tissues,  is  developed  from  Development, 
embryonic  cells.  Those  cells  which  are  about  to  take 
on  the  cartilaginous  transformation,  secrete  from  their 
external  surfaces  an  enveloping  membrane,  which 
becomes  their  capsule,  whilst  a  solid  structureless 
material  is  deposited  around  them,  constituting  the 
fundamental  substance.  In  the  formation  of  fibro- 
cartilage  a  portion  only  of  the  original  formative  cells 
take  on  the  changes  above  described,  whilst  the 
remainder  transform  themselves  into  connective  and 
elastic  fibres. 

The  growth  of  cartilage  is  effected  in  part  by  the  Growth. 
endogenous  multiplication  of  its  cells  (vide  sect.  1, 
chap.  1),  and  in  part  by  the  addition  of  new  tissue  to 


30  CARTILAGE. BONE. TEETH. 

its  surface,  derived  from  ihe  plasmatic  cells  of  the 
perichondrium  as  already  described.  It  lias  not  been 
demonstrated  that  cartilage  is  ever  reproduced  when 
destroyed  by  disease  or  injury ;  it  is  replaced  by 
transformed  plasmatic  cells,  as  far  as  the  process  can 
be  traced.* 

To  study  the  structure  of  cartilage  very  thin  slices 
should  be  cut  from  it  by  means  of  a  razor. 

SECT.  II.  BONE. — To  study  advantageously  the  mi- 
nute anatomy  of  bone,  sections  as  thin  and  delicate 
as  possible,  should  be  made  with  a  saw  in  every  direc- 
tion through  its  substance,  and  the  laminae  thus  pro- 
cured should  be  rubbed  down  with  moistened  pumice 
stone,  and  afterwards  polished  upon  a  fine  whetstone. 
It  is  well  also  to  examine,  in  connexion  with  these, 
the  delicate  and  transparent  scales  which  form  the 
walls  of  the  cancelli  of  the  spongy  portion  of  the  bony 
tissue ;  they  can  be  readily  detached,  and  when  placed 
between  two  slips  of  glass,  and  moistened  with  a  drop 
of  water,  are  ready  for  use. 

structure  of  In  a  transparent  lamina  of  bone  thus  prepared, 

when  placed  under  the  microscope,  there  are  always 
two  elements  to  be  recognised,  and  these  alone  con- 
stitute true  osseous  tissue,  viz.  bone  cells,  and  the 

*  There  are  many  points  connected  with  the  histology  of  cartilage,  and 
especially  of  articular  cartilage,  still  unsettled,  and  in  consequence  of  the 
important  bearing  of  this  knowledge  upon  the  principles  of  surgery,  as 
applied  to  diseases  of  joints,  I  cannot  refrain  from  calling  attention  to  the 
admirable  papers  of  Mr.  R.  Harwell,  F.R.C.S.E.,  Ast.  Surgeon  Charing 
Cross  Hosp'l,  Lond.,  in  the  No.  for  October,  1859,  of  the  Medico- Chirur- 
gical  Review,  and  in  the  No.  for  February,  1860,  of  the  Edinburgh  Me- 
dical Journal.  They  are  complementary  to  the  researches  of  Ecker, 
Goodsir,  and  Redfern,  and  comprise  the  fullest  knowledge  of  the  subject 
yet  acquired  by  science. — (Ed?) 


CARTILAGE. BONE. TEETH.  81 

medium  in  which  they  are  found,  which  we  shall 
designate  as  the  fundamental  substance  of  hone.  This 
latter  consists  of  a  whitish  structureless  material — 
opaque,  or  transparent,  according  to  the  thickness  of 
the  section.  It  is  composed,  chemically,  of  earthy 
salts,  and  an  organic  substance  by  means  of  which  the 
earthy  particles  are  held  together. 

The  cells  of  bone  (called  also  osseous  corpuscles, 
osteo-plastic  cells,  and  laounce)  bear  some  resemblance 
in  their  shape  and  outline  to  the  star-shaped  or 
branching  plasmatic  cells  already  described.  They 
are  minute  fusiform  bodies,  slightly  flattened  laterally, 
and  measuring  from  TJ7th  to  T~d  of  a  line  in  length. 
From  their  exterior  a  delicate  tracery  of  minute 
thread-like  prolongations  radiate  in  every  direction, 
anastomosing  with  each  other,  and  with  those  of  neigh- 
boring cells.  Under  a  magnifying  power  of  from  350 
to  400  diameters  it  can  be  distinctly  seen  that  these 
filiform  appendages  of  the  cells  of  bone  are  hollow  in 
their  interior,  and  are,  in  fact,  very  minute  tubes  or 
canaliculi ;  their  mode  of  communication  is  likewise 
very  apparent,  (PL  V.  fig.  IV).  The  more  delicate 
scales  of  the  spongy  variety  of  bone,  and  the  cemen- 
tum  of  the  teeth,  present  in  fact  no  other  constituent 
elements ;  but  this  is  not  true  of  the  more  dense  or 
cortical  substance  of  bone,  or  of  scales  of  greater  thick- 
ness. On  placing  a  transverse  section  of  a  long  bone 
under  the  microscope,  it  is  at  once  apparent  that  its 
cells  are  grouped  after  a  certain  fixed  plan.  In  fact 
they  are  arranged  very  regularly  in  concentric  circles 
around  a  larger  central  opening — which  is  the  trans- 
verse section  of  the  track  of  a  blood-vessel,  or  in  other 


32  CARTILAGE. BONE. TEETH. 

words,  a  Haversian  canal.  Very  many  of  the  canaliculi 
from  the  nearest  circle  of  bone-cells  are  also  to  be  seen 
running  into  the  Haversian  canal.  In  the  long  bones 
the  Haversian  canals  run  parallel  with  the  axis  of  the 
shaft  of  the  bone,  and  communicate  with  each  other 
at  short  intervals  by  transverse  anastomotic  branches 
(PL  VI.  fig.  I.  1,  2,  3).  In  the  short  and  flat  bones 
they  also  pursue  a  determinate  course,  and  anastomose 
in  a  similar  manner.  These  canals,  which  contain 
the  bloodvessels  of  the  osseous  tissue,  tunnel  its  fun- 
damental substance  in  all  directions,  terminating 
either  upon  the  external  surface  of  the  bone,  or  in  its 
medullary  cavities.  The  nutrition  of  bone  is  effected 
by  means  of  the  parts  just  described.  The  very 
numerous  orifices  of  the  canaliculi  in  the  walls  of  the 
Haversian  canal  receive  the  nutritious  fluid  which 
exudes  through  the  walls  of  its  contained  bloodvessel, 
and  convey  it  throughout  the  network  which  they 
and  their  parent  bone-cells  or  lacunae  form,  to  the 
outermost  of  the  series  of  concentric  circles, 
periosteum,  The  fibrous  membrane  which  invests  bone  exter- 
nally, called  periosteum^  resembles  perichondrium  in 
its  structure ;  it  is  an  interlacement,  or  rather  a  felting, 
of  connective  and  elastic  fibres,  traversed  by  some 
nerves  and  very  numerous  bloodvessels,  and  studded 
with  plasmatic  cells  which,  as  we  shall  see,  play  an 
important  part  in  the  formation  and  growth  of  bone. 
(PL  VI.  fig.  V.)  ' 

tiees(hlll8iy  e**~  ^e  medullary  cavities  of  bones  are  filled  by  mar- 
row, which  is  in  direct  contact  with  their  walls,  for 
the  prevalent  idea  that  the  walls  of  these  cavities  are 
lined  by  an  internal  periosteum,  or  medullary  mem- 


CARTILAGE. BONE. TEETH.  33 

brane,  is  incorrect.  These  names  have  been  applied 
to  the  scattered  fasciculi  of  connecting  tissue  by  which 
the  blood-vessels  and  fat  cells  of  the  marrow  are  sup- 
ported. 

Marrow  is  found  only  in  the  cancelli  and  medul-  Marrow, 
lary  canals  of  bone ;  neither  the  Haversian  canals 
nor  the  canaliculi  contain  it.  In  the  foetus  it  is  of  a 
reddish  color  and  possesses  some  consistency ;  in  the 
adult  it  is  met  with  in  this  form  only  in  the  smaller 
cancelli  of  spongy  bone,  and  in  short  and  flat  bones ; 
in  the  medullary  canals  of  long  bones,  and  in  the 
larger  cancelli  of  their  spongy  substance,  it  is  yellow 
in  color  and  almost  diffluent.  Thus,  there  are  two 
varieties  of  marrow,  which  differ  in  their  histologi- 
cal  elements  as  well  as  in  their  physical  properties. 
The  red,  or  foetal  marrow,  is  made  up  of  an  aggre- 
gation of  spherical  cells,  each  containing  fine  granular 
matter  and  one  large  nucleus.  Some  of  these  cells  have 
several  nuclei,  and  attain  a  large  size  (TVth  to  TVth 
of  a  line).  It  is  worthy  of  remark,  in  passing,  that 
the  cells  of  foetal  marrow'  are  identical  in  appearance 
with  certain  forms  of  so-called  cancer  cells.  This 
variety  of  marrow  is  richly  supplied  with  blood-ves- 
sels, which  traverse  its  substance,  accompanied  by 
delicate  filaments  of  connecting  tissue. 

The  cells  of  yellow  marrow  are  nothing  more  than 
vesicles  filled  with  liquid  *fat,  or  ordinary  fat  cells. 
In  some  of  them  the  nucleus  can  be  still  recognised, 
and  others  again  resemble  so  closely  the  cells  of  foetal 
marrow  as  to  suggest  a  series  of  transitional  changes, 
by  which  it  is  rendered  probable  that  the  ordinary 
yellow  marrow  is  nothing  more  than  foetal  marrow. 


Arteries  and 
nerves  of  bone. 


34  CARTILAGE. — BONE. TEETH. 

the  cells  of  which  have  undergone  the  process  of  fatty 
degeneration. 

Of  the  two  varieties  the  red,  or  foetal  marrow,  is 
more  richly  supplied  with  blood-vessels. 

The  arteries  of  bone  are  derived  from  its  perios- 
teum; one  class  of  them,  the  smaller  vessels,  pene- 
trate the  compact  substance  and  pursue  the  same 
course  as  the  Haversian  canals  which  they  occupy ; 
the  other  class,  larger,  and  known  as  nutritious  arte- 
ries, enter  separate  canals  of  their  own,  and  thus 
reach  the  medullary  cavities,  where  they  terminate 
by  supplying  the  marrow  and  anastomosing  with  the 
vessels  of  the  first  class.  The  veins,  as  a  rule,  present 
the  same  calibre  and  pursue  the  same  course  as  the 
arteries  with  which  they  correspond ;  in  some  instan- 
ces, however,  they  assume  a  larger  size  and  different 
arrangement,  as  in  the  sinuses  of  the  diploe,  and  of 
the  bodies  of  the  vertebrae.  Up  to  the  present  time 
lymphatics  have  not  been  demonstrated  in  bone.  Its 
nerves,  which  are  numerous,  ordinarily  follow  the 
course  of  the  arteries,  and  supply  the  marrow  as  well 
as  the  bone;  before  penetrating  its  substance  they 
give  off  branches  to  the  periosteum.  There  is  reason 
to  believe  that  they  terminate  by  free  extremities. 
bonveelopmont  of  ^ne  development  and  growth  of  bone  is  accom- 
plished in  two  ways :  by  ossification  of  the  cartila- 
ginous skeleton  of  the  fcetus/  and  by  transformation 
of  the  deeper  layers  of  the  periosteum. 

The  first  mode  of  development  is  best  studied  in 
very  thin  sections  of  a  young  bone,  made  just  at  the 
line  of  junction  of  the  cartilage  and  bone.  On  exa- 
mining, in  the  first  place,  the  cartilaginous  portion  of 


CAETILAGE. BONE. TEETH.  35 

the  section,  it  is  to  be  observed  that  its  cells  are  dis- 
posed in  parallel  rows,  and  that  some  of  them  are 
quite  altered  in  appearance.  One  portion  of  them 
differs  in  no  respect  from  ordinary  cartilage  cells, 
whilst  the  remainder  have  already  changed  in  form, 
the  change  being  confined  mainly  to  their  nuclei. 
The  nucleus,  for  example,  has  become  very  irregular 
in  its  outline,  and  by  sending  out  prolongations  in 
every  direction,  has  put  on  a  decided  resemblance  to 
a  bone-cell.  It  is  imbedded  in  a  finely  granular  sub- 
stance limited  by  a  pale  circular  or  oval  line,  the  cell 
wall ;  outside  of  this  another  line  is  to  be  seen  in 
close  proximity  to  the  first,  and  surrounding  the  cell ; 
this  is  the  capsule  of  the  cartilage  cell.  (PL  VI.  fig. 
III.  2,  3,  4.) 

In  view  of  these  facts  it  is  pretty  evident  that  the 
osseous  cell,  or  lacuna,  is  identical  with  the  nucleus 
of  the  original  cartilage  cell,  in  a  more  advanced 
stage  of  development. 

The  process  of  ossification  is  completed  by  the 
elongation  of  the  filiform  prolongations,  or  canaliculi, 
given  off  from  the  nuclei  of  the  cartilage  cells,  which 
terminate  by  anastomosing  with  the  canaliculi  of 
neighboring  nuclei ;  and  meanwhile  earthy  salts  have 
been  brought  by  the  bloodvessels  and  deposited  in 
the  fundamental  substance  of  the  cartilage,  as  well  as 
in  the  interior  of  its  cells.  Neither  the  walls  of  these 
cells,  nor  their  enveloping  capsule,  disappear  imme- 
diately after  the  ossification  of  their  contents  ;  by  the 
addition  of  dilute  hydrochloric  acid  to  a  portion  of 
recently  ossified  bone  they  can  both  be  rendered 
visible — prssenting  their  usual  appearance. 


36  CARTILAGE. BONE. TEETH. 

It  is  asserted  by  some  observers  that  it  is  the  car- 
tilage cells  themselves,  and  not  their  nuclei,  which 
are  thus  transformed  into  bone  cells.  They  describe 
the  cell-wall  as  becoming  wrinkled,  and  undergoing 
the  changes  which  we  have  attributed  to  its  nucleus, 
whilst  the  nucleus  itself  fades  away  and  finally  dis- 
appears entirely.  (PL  VIL  fig.  II.)  In  opposition  to 
the  authorities  by  whom  this  statement  is  endorsed, 
we  are  disposed  to  persist  in  the  belief  that  it  is  the 
nucleus  of  the  cartilage  cell  which  becomes  trans- 
formed into  the  osseous  cell,  or  lacuna,  of  bone. 
F<etai  Marrow.  The  cells  of  ossifying  cartilage  which  remain  un- 
changed during  the  process  just  described,  eventually 
assume  the  character  of  foetal  marrow.  At  first  they 
become  the  seat  of  active  endogenous  development, 
in  consequence  of  which  they  increase,  together  with 
their  enveloping  capsules,  very  considerably,  in  size. 
PL  VI.  fig.  IV.  4.)  Very  soon  they  come  in  contact 
with  each  other,  their  capsules  becoming  welded 
together  (PL  IV.  5),  and  the  partitions  which  thus 
result,  melting  away  as  they  lie  arranged  in  longi- 
tudinal rows,  a  medullary  canal  is  thus  formed  filled 
with  young  cells  and  free  oil-globules,  wrhich,  in  fact, 
constitutes  foetal  marrow.  (PL  IV.  6.)  Whilst  the 
process  of  ossification  is  going  on,  numerous  blood- 
vessels derived  from  its  perichondrium  are  seen 
ramifying  through  the  substance  of  the  cartilage. 
These  seem  at  first  to  be  simply  hollowed  out  of  the 
cartilage  ;  but  later  in  the  process  the  cartilage  cells 
immediately  around  them  become  elongated  and  fusi- 
form in  shape,  and  seem  by  their  subsequent  union 
to  form  walls  for  the  vessels. 


CAKTILAGE. BONE. TEETH.  3  7 

The  process  of  ossification  from  periosteum  is  less 
complicated  than  that  just  described,  by  which  car- 
tilage is  converted  into  bone.  This  fibro-vascular 
membrane  contains,  as  we  have  already  stated,  a  large 
number  of  little  star-shaped  or  plasmatic  cells. 
When,  by  the  addition  of  acetic  acid,  the  ordinary 
connective  fibres  of  the  membrane  are  made  to  dis- 
appear, more  than  one  layer,  composed  of  elastic  fibres 
and  branching  cells,  is  brought  in  view,  in  which 
both  the  form  and  arrangement  of  osseous  cells  are 
faithfully  represented.  (PL  VII.  fig.  1,  3.)  In  the 
deepest  layers  of  the  periosteum,  where  ossification 
takes  place,  the  plasmatic  cells  are  seen  to  be  more 
numerous,  and  farther  advanced  in  development  than 
elsewhere.  The  blastema  in  which  they  are  imbedded 
is  also  deeper  in  color,  and  this  is  explained  by  the 
presence,  already,  of  earthy  salts.  (PL  VI.  fig.  V.  2, 
3.)  In  fact  the  process  of  ossification  is  thus  almost 
perfected,  for  the  plasmatic  cell  requires  only  to  be 
imbedded  in  and  surrounded  by  earthy  matter,  to 
become  a  cell  of  bone.  However,  the  process  is  not 
always  effected  in  so  simple  a  manner,  for  sometimes 
the  plasmatic  cells  do  not  present  their  usual  star- 
shaped  prolongations,  and  in  this  case  the  filiform 
processes,  which  ultimately  form  canaliculi,  only  make 
their  appearance  whilst  the  incrustation  of  their  cell- 
walls  is  actually  taking  place. 

From  our  own  investigations  it  is  evident  that  the 
ossification  of  the  cranial  bones  is  effected  entirely  by 
the  changes  just  delineated  in  their  periosteal  cover- 
ings. (PL  VII.  fig.  I.)  The  new  deposits  of  bony 
matter  which  take  place  in  some  grades-  of  perios- 


38  CARTILAGE. BONE. TEETH. 

teal  inflammation  are  explained  in  the  same  man- 
ner. 

separation  of  The  reparation  of  bones  after  fracture  or  exsec- 
tion,  or  where  a  portion  has  been  gouged  out  in  an 
operation,  is  accomplished  by  a  process  analogous  to 
that  which  the  periosteum  performs  in  ossification. 
The  gelatiniform  mass  which  forms  between  the  frag- 
ments of  a  broken  bone,  in  an  excavation  produced 
by  the  gouge,  or  even  in  a  medullary  cavity,,  contains 
usually  some  fibrillae  of  connective  tissue,  together 
with  a  large  number  of  blood-globules  and  oval 
nuclei  (fibro-plastic),  which  are  subsequently  con- 
verted into  bone  cells.  It  is  easy  to  follow  the  suc- 
cessive transformations  of  these  nuclei  by  the  micro- 
scopic examination  of  a  very  thin  lamella  of  bone  to 
which  this  gelatiniform  material  is  still  adherent. 
These  are  the  several  steps  of  the  process  :  at  a  little 
distance  from  the  bone,  the  oval  nuclei  possess  a  very 
regular  outline,  but  as  we  trace  them  nearer  to  its 
surface  they  are  observed  to  change  their  shape ; 
their  outlines  wrinkle,  and  send  out  linear  prolonga- 
tions radiating  in  every  direction;  at  the  same  time 
earthy  matter  is  deposited  around  them,  by  which 
they  become  gradually  encrusted,  and  thus  the  meta- 
morphosis into  bone  is  completed.  (PL  XXVII. 

4 1.) 

Reparation  or  reproduction  of  bone  in'  a  medullary 
canal,  and  in  the  cancelli  of  its  spongy  portions,  is 
not  accomplished  by  medullary  membrane,  which,  as 
we  have  already  asserted,  has  no  existence,  nor  yet 
by  the  aid  of  an  imaginary  cartilage,  which,  in  any 
case,  would  be  but  transitory.  The  phenomena  of 


CAETILAGE. BONE. TEETH.  39 

ossification  here  are  entirely  analogous  to  those  we 
have  observed  in  the  deeper  strata  of  periosteum, 
both  in  its  healthy  state,  and  when  inflamed.  In  all 
these  cases  the  osseous  cell,  in  the  absence  of  which 
the  tissue  of  bone  cannot  exist,  is  developed  from 
another  cell  or  its  nucleus — that  is  to  say  from  the 
essential  organic  element — which  is  always  present 
both  in  the  periosteum,  and  in  the  contents  of  the 
medullary  cavities. 

SECT.  III. — TEETH.  A  tooth  consists  of  a  central  Teeth, 
portion  which  constitutes  nearly  the  whole  of  the 
organ,  and  of  an  outer  lamina  which  accurately  invests 
its  external  surface.  The  central  mass,  or  ivory,  has 
a  cavity  in  its  interior — variable  in  size  and  shape, 
which  communicates  externally  through  a  narrow 
canal  situated  at  the  extremity  of  the  root;  this 
cavity  contains  the  pulp  (PL  VIII,  fig.  I.  1,  2).  The 
portion  of  the  external  lamina  which  invests  the 
crown  of  the  tooth  is  the  enamel  (fig.  I.  4) ;  that 
which  covers  its  root  is  the  cementum  (fig.  I.  3). 

The  ivory  is  composed  of  fundamental  substance,  ivory, 
traversed  by  minute  canals.  The  former,  structure- 
less and  transparent  when  viewed  in  thin  section,  is 
identical  with  the  fundamental  substance  of  bone,  and 
the  canals  which  it  contains  resemble  closely  the 
'canaliculi  of  bone-cells.  They  take  their  origin  in 
the  central  cavity  of  the  tooth,  and  thence  radiate  to 
the  surface  of  the  ivory,  where  they  terminate ;  it  is 
an  exception  to  the  rule  for  them  to  pass  beyond  this 
limit  and  to  penetrate  the  exterior  lamina  (PL  VIII. 
fig.  III.  2).  At  their  commencement  some  are  single, 
others  arise  from  a  common  trunk,  and  others  again 


40  CAETILAGE. BONE. TEETH. 

take  their  origin  from  minute  cavities  in  the  deeper 
strata  of  the  fundamental  substance;  these  latter, 
however,  always  communicate  with  the  central  cavity 
of  the  tooth  (PL  VIII.  fig.  II.  4).  With  a  magni- 
fying power  of  350  to  400  diameters,  the  canals  can 
be  seen  to  be  sharply  limited  by  two  very  fine  but 
distinct  lines,  to  be  slightly  wavy  or  undulating  in 
their  course,  and  to  run,  mainly,  parallel  to  each 
other.  Their  lateral  branches  can  also  be  distin- 
guished, radiating  in  every  direction,  anastomosing 
with  each  other,  and  thus  forming  an  universal  net- 
work, which  permeates,  everywhere,  the  fundamental 
substance  of  the  ivory.  (PL  VII.  fig.  III.  1,  2  ;  PL 
VIII.  fig.  II). 

At  their  origin  the  canals  are  larger  than  at  their 
termination,  measuring,  on  an  average,  from  r-nrcrth 
to  T^o-th  of  a  line.  Sometimes  they  present,  in  their 
course,  small  spindle-shaped  enlargements  (PL  VIII. 
fig.  II.  3),  and  they  terminate,  as  a  rule,  in  irregularly 
shaped  cavities  which  are  the  interspaces  between 
minute  glob  .  ar  masses  of  the  fundamental  substance 
(PL  VIII.  ng.  II.  5).  It  is  to  be  noticed  that  these 
inter-globular  spaces,  as  they  have  been  designated, 
communicate  freely  with  the  bone-cells  of  the  cemen- 
tum,  to  which,  in  fact,  they  bear  no  little  resem- 
blance. 

Enamel.  The  'enamel  forms  a  hard  and  homogeneous  lamina 
moulded  accurately  upon  the  surface  of  the  crown  of 
the  tooth,  and  terminating,  at  its  neck,  by  a  thin 
edge,  which  seems  to  insinuate  itself  between  the 
ivory  and  the  terminal  margin  of  the  cementum.  It 
is  composed  exclusively  of  five  or  six-sided  prisms, 


CAETILAGE. BONE. TEETH.  41 

placed  side  by  side,  without  any  appreciable  inter- 
vening substance  (PL  VIII.  fig.  IV.  1).  Examined 
in  vertical  section  they  are  observed  to  undulate 
slightly,  and  to  assume  a  direction  perpendicular  to 
the  nearest  surface ;  moreover,  they  are  generally 
parallel  with  each  other,  except  upon  the  irregularly 
shaped  surfaces  of  the  molar  teeth,  where  they  form 
divergent  bundles  (PL  VIII.  fig.  III.).  Their  sub- 
stance is  wholly  amorphous ;  sometimes  it  is  crossed 
by  transverse  lines  ;  its  chemical  nature  seems  to 
connect  it  with  the  epithelial  formations.  Some 
observers  have  asserted  that  the  enamel  is  invested 
externally  by  a  delicate  structureless  layer,  which 
they  designate  as  the  cuticle  of  the  enamel. 

The  cementum,  by  which  the  root  of  the  tooth  is 
covered  externally,  is  true  bone ;  it  consists  of  funda- 
mental substance,  and  bone-cells  of  variable  size  and 
irregular  in  their  arrangement.  Haversian  canals  are 
absent,  except  where  its  structure  has  been  altered 
by  inflammation.  The  periosteal  investment  of  the 
alveolar  sockets  also  covers  the  surface  of  the  ce- 
mentum. 

The  pulp  of  the  tooth,  which  occupies  its  central  r>entaipuip. 
cavity,  is  connected  with  the  periosteum  of  the  socket 
by  a  pedicle   which  penetrates   the  orifice   at   the 
pointed  extremity  of  its  root.     It  is  made  up  of  deli- 
cate connective  tissue,   interspersed  with  plasmatic 
cells,    and  largely   supplied    by   blood-vessels    and 
nerves — the  terminal  arrangement  of  the  latter  being, 
as  yet,  imperfectly  made  out.     The  presence  of  lym-^ 
phatic  vessels  in  the  pulp  is  uncertain.     During  the  Development  of 
sixth  week  of  foetal  life,  the  free  borders  of  the  niax- 

3 


42  CAETILAGE. BONE. TEETH. 

illary  bones  begin  to  show  distinct  longitudinal 
depressions  or  grooves,  at  the  bottom  of  which  minute 
granulations  make  their  appearance,  which  are  the 
germs  of  the  teeth  ;  it  is  from  these  that  the  ivory  is 
developed.  Shortly  afterwards  partitions  make  their 
appearance  by  which  the  groove  is  divided  up  into 
separate  apartments,  with  a  germ  at  the  bottom  of 
each — recalling  in  their  appearance  the  circumvallate 
papillae  of  the  tongue.  Still  later  the  margins  of 
these  compartments,  as  they  grow,  rise  above  the 
level  of  the  germs,  contract  by  approaching  from 
opposite  sides,  and  finally  unite  together.  Hereafter 
the  germ  is  enveloped  on  all  sides  in  a  cavity  which 
takes  the  name  of  the  dental  sac. 

Dental  sac.  The  walls  of  the  sac  are  at  first  formed  by  two  dis- 
tinct layers,  which  afterwards  become  one.  The 
external  layer,  which  later  becomes  the  periosteum 
of  the  socket,  is  made  up  of  very  vascular  connecting 
tissue ;  the  internal  layer,  of  the  same  nature  as  the 
preceding,  but  more  delicate  in  structure,  contri- 
butes, according  to  M.  Magitot,*  to  the  subsequent 
formation  of  the  enamel. 

We  know  already  that  the  dental  germ  takes  its 
origin,  by  a  pedunculated  root,  from  the  bottom  of 
the  sac ;  from  a  point  diametrically  opposite  to 
this  springs  another  germ  similar  to  it  in  nature, 
which,  as  we  shall  see  hereafter,  gives  origin  to  the 
enamel. 
of  The  dental  germ  (whence  the  ivory  is  developed) 

*  Emile  Magitot  has  a  paper  on  the  structure  of  the  teeth  in  the 
Archives  Medicates,  Paris,  Jan.  1858,  and  has  sinoe>ritten  on  the  subject 
in  same  Journal.— (Ed.} 


CAKTILAGE. BONE. TEETH.  43 

rich  in  blood-vessels,  which  reach  it  through  its  pedi- 
cle, contains,  besides,  a  large  number  of  nuclei  and 
young  cells  of  an  oval  •  form,  together  with  some 
connective  fibrillae ;  its  nerves,  which  appear  some- 
what later,  accompany  its  vessels.  It  is  covered  by 
an  amorphous  membrane*  which,  as  Magitot  has 
shown,  is  incorrectly  regarded  as  a  portion  of  the 
internal  layer  of  the  wall  of  the  dental  sac.  This 
border  belongs  really  to  the  germ,  and  takes  no  part 
in  the  subsequent  formation  of  the  ivory.  Beneath 
this  there  is  a  stratum  of  oval  cells,  arranged  very 
regularly  side  by  side,  with  their  long  diameters  per- 
pendicular to  the  surface  of  the  germ.  The  peripheral 
extremity  of  each  cell  elongates  into  a  thread-like 
tube,  which  by  degrees  increases  in  size,  and  gives  off 
minute  lateral  branches ;  in  this  manner  a  great 
number  of  minute  canals  are  formed,  which  run 
parallel  with  each  other  to  the*  extreme  limit  of  the 
germ,  communicating  largely  by  their  ramifications. 
Thus  the  canalicuii  of  the  ivory  of  the  tooth  are 
developed  from  the  superficial  cells  of  its  germ,  each 
cell,  according  to  Kolliker,f  by  a  process  similar  to 
wire-drawing,  elongating  itself  into  a  complete  canal. 
Whilst  the  dental  canals  are  being  thus  developed, 

*  Homogeneous  basement  membrane  of  Todd  and  Bowman.  In  his 
account  of  the  development  of  the  teeth  the  author  mainly  follows 
Goodsir.— (Ed.} 

t  A.  Kolliker,  Professor  of  Anatomy  and  Physiology  in  the  University 
of  Wufzburg  (Bavaria),  author  of  the  "  Manual  of  Human  Microscopic 
Anatomy,"  which  has  been  twice  translated  into  English ;  first  by  Pro- 
fessors Busk  and  Huxley,  and  published  by  the  Sydenham  Society, 
1853-54;  and  more  recently,  in  a  revised  edition,  by  Dr.  George 
Buchanan,  under  the  author's  supervision.  Parker,  London.  1860. 


44  CAKTILAGE. BONE.  —TEETH. 

an  amorphous  substance  is  poured  out  in  the  intervals 
between  them,  an  exudation  furnished,  no  doubt,  by 
the  deeper  cells  of  the  germ,  and  which  subsequently 
becomes  the  fundamental  substance  of  the  ivory  of 
the  tooth.  Finally,  its  development  is  completed  by 
the  infiltration  of  the  fundamental  substance  with 
calcareous  salts,  and  what  remains  of  the  original 
Development  germ  becomes  atrophied  and  forms  the  dental  pulp. 
The  germ  of  the  enamel,  having  attained  its  com- 
plete development,  envelopes  entirely  the  base  of  the 
germ  of  the  ivory,  which  we  have  traced  to  its  com- 
plete ossification.  Superficially  it  is  made  up  of  con- 
necting tissue  rich  in  blood-vessels ;  more  deeply 
there  are  only  star-shaped  cells  imbedded  in  amor- 
phous material ;  and  finally  the  stratum  immediately 
in  contact  with  the  dental  germ,  is  formed  by  an 
epithelial  layer,  whose  cells,  long,  narrow,  and  pris- 
matic in  shape,  resemble  closely  the  prisms,  already 
described,  of  the  enamel.  Thus  it  is  more  than  pro- 
bable that  the  enamel  is  formed  directly  by  the 
°f  petrifaction  of  these  elementary  bodies.  The  lower 
partions  of  the  dental  sac  give  origin  to  the  cemen- 
tum,  taking  on  the  process  of  ossification  in  the  same 
manner  as  periosteum. 

In  view  of  the  fact  that  connecting  tissue,  under 
certain  circumstances,  undergoes  transformation  into 
cartilage  and  bone,  as  well  as  into  the  substance  of 
the  teeth,  these  tissues,  being  all  analogous  in  nature, 
are  grouped  together,  by  some  authorities,  in  one 
family. 

The  preparations  required  for  the  study  of  the 
structure  of  the  teeth  are  prepared  in  the  same  man- 
ner a*s  sections  of  bone. 


CHAPTER    IV. 
Muscular    Tissue. 

THE  essential  element  of  muscular  tissue,  i.e.  the 
contractile  element,  presents,  in  its  intimate  structure, 
both  cells  and  fibres.  The  cell  is  a  transitory  ele- 
ment, or  rather  is  found  only  in  those  organs  in  which 
an  incomplete  stage  of  development  is  persistent. 
The  fibre,  in  two  distinct  forms,  constitutes  the  bulk 
of  all  recognised  muscles.  The  two  varieties  are 
known  as  the  striped,  and  the  smooth  or  unstriped 
muscular  fibre. 

Smooth,  or  unstriped  muscle. — When  a  small  por-  structure  of 

smooth    muscu- 

tion  of  certain  muscular  organs,  the  muscular  wall  of  larfU)re- 
the  intestine,  or  of  the  bladder,  for  example,  is  placed 
beneath  the  microscope,  it  is  found  to  consist  appa- 
rently of  long,  pale,  spindle-shaped  bodies,  each  one 
of  which  is  provided  with  an  elongated  nucleus 
having  a  clear  and  distinctly  marked  outline,  and 
surrounded  by  a  substance  so  finely  granular  as  to 
appear  almost  amorphous.  More  attentive  exami- 
nation, however,  reveals  the  real  nature  of  these 
nucleated  bodies — the  essential  contractile  elements ; 
in  place  of  a  spindle-shaped  cell,  it  is  soon  recognised 
as  a  true  fibre,  presenting,  as  we  trace  it  in  the  direc- 
tion of  its  length,  a  regular  succession  of  contractions 
and  enlargements.  These  fibres,  instead  of  running 
parallel  with  each  other,  cross  at  very  acute  angles, 
and  in  such  a  manner  that  their  points  of  intersection 


46  MUSCLES. 

a 

seem  to  correspond  always  with  their  narrow  or  con- 
tracted intervals,  or,  as  it  is  still  described  by  some, 
with  the  tapering  points  of  the  fibre-cells.  A  cir- 
cumstance which  has  doubtless  served  to  perpetuate 
this  erroneous  view  is  that  these  fibres  break  very 
easily  when  an  attempt  is  made  to  isolate  them,  and 
as  the  rupture  always  -takes  place  at  one  of  the  con- 
stricted portions  of  the  fibre,  which  tapers  off  as  it 
breaks,  in  consequence  of  its  elasticity,  it  results  that 
each  fragment  thus  detached  presents  a  regular  spin- 
dle shape.  (PL  XIV.  fig.  VIII.)  But  if  a  section  is 
made  across  the  course  of  the  fibres,  polygons  are 
brought  into  view,  varying  very  considerably  in  dia- 
meter (jioth  to  lioth  of  a  line),  but  never  of  a  size 
so  small  as  to  be  recognisable  as  the  terminal  point 
of  a  spindle-shaped  corpuscle.  (PI.  IX.  fig.  II.)  The 
same  section  shows  also  the  mode  in  which  these 
fibres  are  grouped  together  so  as  to  form  fasciculi  of 
muscle.  Between  the  fibres  which  are  thus  in  imme- 
diate contact  with  each  other,  forming  fasciculi,  there 
is  no  intervening  substance  whatever ;  but  they  are 
surrounded  by  an  investment,  or  sheath,  of  connecting 
tissue  which  also  includes  the  blood-vessels  and  ner- 
vous filaments  by  which  they  are  supplied.  (PI.  IX. 
fig.  II.  4.) 

contractile  ceiiB.  The  contractile  fusiform  element,  or  fibro- cellular 
corpuscle,  is  found  only  in  those  organs  whose  nor- 
mal condition  is  one  of  imperfect  development — as 
for  example,  in  the  smallest  arteries,  of  a  diameter  of 
from  7V th  to  ?Vth  of  a  line.  In  vessels  of  this  class 
the  middle  or  muscular  coat  consists  of  this  element 
in  its  purest  form.  It  is  not  difficult  to  demonstrate 


MUSCLES.  .  4 

that  the  contractile  element  of  which  it  is  composed 
is  a  spindle-shaped,  or  fusiform,  corpuscle  of  variable 

length,  in    the   interior  of  which  a  nucleus,  which 

. 
approaches  more  nearly  the  circular  shape  than  that 

of  the  true  smooth  or  unstriped  fibre,  is  recognisable, 
(PL  XV.  fig.  VII.  2,  3.)  We  find  this  fusiform  cor- 
puscle in  the  walls  of  the  villi  of  the  small  intestine, 
in  the  muscles  of  the  hair-bulbs,  and  perhaps  also  in 
other  organs.  It  is  as  yet  an  unsettled  question 
whether  the  dartos  is  made  up  of  this  element,  or  of 
the  fully  developed  unstriped  fibre. 

The  distribution  of  the  smooth,  or  unstriped  mus-  Distribution   of 

smooth  muscular 

cular  tissue,  limited  at  first  to  organs  possessed  of 
obvious  contractility,  is  daily  increasing  in  extent. 
Thus,  its  presence  has  been  demonstrated  in  the  villi 
of  the  intestines,  in  the  excretory  ducts  of  most  of  the 
glands,  in  the  middle  coat  of  arteries,  veins,  and  lym- 
phatics, in  the  genital  organs  of  the  female  (uterus 
and  appendages,  vagina,  and  corpora  cavernosa  of  the 
clitoris)  ;  in  the  genital  organs  of  the  male  (corpora 
cavernosa  penis,  prepuce,  prostate,  seminal  vesicles, 
&c  )  ;  in  the  vascular  tunic  of  the  eye  ;  and,  finally, 
throughout  the  whole  extent  of  the  skin,  where  it  is 
very  unequally  distributed.  It  is  found  in  connexion 
with  the  hair-bulbs  and  sebaceous  follicles ;  and  by 
its  presence,  the  phenomenon  of  horripilation,  or 
goose-flesh,  is  explained.  Some  portions  of  the  ex- 
ternal integument  are  unusually  rich  in  unstriped 
muscular  fibres ;  for  example,  the  prepuce,  and  the 
skin  of  the  nipple,  and  in  some  instances,  of  the  whole 
female  breast.  The  elongation  and  rigidity  of  the 
nipple  are  due  entirely  to  their  contraction,  and  not, 


48 


MUSCLES. 

* 


Development  of 
unstriped  muscu- 
lar fibre. 


as  generally  supposed,  to  a  turgescence,  or  erection, 
similar  to  that  of  the  corpora  cavernosa. 

Smooth,  or  unstriped  muscular  fibres  are  developed 
from  formative  cells,  which  at  first  elongate,  and  then 
become  attached  by  their  extremities.  In  some  organs 
and  localities  this  mode  of  development  is  incom- 
plete ;  the  metamorphoses  of  the  formative  cells  are 
arrested  in  their  earlier  stages,  and  thus  the  exist- 
ence of  the  contractile  fusiform  corpuscle — the  fibre- 
cell  of  Kolliker,  is  explained.  Hereafter  we  shall 
see  that  the  true  striped  muscular  fibre  passes  through 
the  two  stages  we  have  just  described  before  it 
assumes  its  ultimate  and  definite  form,  so  that,  in  a 
general  histological  survey  of  the  entire  muscular 
tissue  of  the  body,  it  may  be  considered  as  repre- 
senting, in  its  several  constituent  portions,  different 
and  progressive  degrees  of  development  of  the  same 
formative  element — of  which  the  striped  fibre  is  the 
last  and  most  perfect  form. 

In  the  muscular  tissue  of  the  uterus  during  preg- 
nancy we  recognise  the  development  of  new  muscular 
fibre  of  the  smooth  variety.  According  to  Kol- 
liker this  takes  place  only  during  the  first  six  months 
of  gestation.  In  its  deeper  strata  an  immense  num- 
ber of  cells  is  recognisable,  measuring  from  T^orth  to 
sVth  of  a  line,  and  we  can  trace  them  through  the 
several  phases  of  their  development  into  smooth  mus- 
cular fibres.  After  delivery,  and  whilst  the  uterus  is 
diminishing  in  bulk,  the  larger  proportion  of  these 
muscular  fibres  become  infiltrated  with  fat,  break 
down,  and  disappear  entirely  by  absorption  ;  it  is  by 
this  process  of  fatty  atrophy  that  the  uterus  returns, 
after  child-birth,  to  its  original  dimensions. 


MUSCLES.  49 

i 

Striped  Muscle. — The  tissue  of  muscle  in  its  sim- 
plest element — the  primitive  fibre — is  variable  in  its 
physiognomy,  presenting  to  the  eye  but  two  con- 
stant features,  viz :  an  external  envelope,  with  con- 
tents marked  by  transverse  stripes.  (PL  IX.  fig.  V. 
and  PL  X.) 

The  primitive  fibre  is  usually  polygonal,  rarely  striped  fibre. 
cylindrical ;  its  envelope,  called  myolemina  or  sarco- 
lemma,*  is  readily  recognisable,  either  without  any 
previous  preparation,  or  by  the  aid  of  chemical  re- 
agents, as  a  perfectly  structureless  membrane.  Nei- 
ther in  the  living  nor  dead  fibre,  neither  in  the  state 
of  contraction  nor  of  relaxation,  can  any  folds  or 
wrinkles  be  detected  in  it  corresponding  with  the 
cross  stripings  of  its  contents.  On  its  internal  sur- 
face, at  regular  intervals,  oval  nuclei  (PL  X.  fig.  II.  3  ; 
PL  IX.  fig.  V.  3)  are  visible — the  last  traces  of  the 
cellular  origin  of  muscle.  It  is  exceedingly  elastic. 

On  examining  its  contents,  the  most  marked  fea- 
tures observed  are  the  transverse  stripes,  equidistant 
from  and  parallel  with  each  other.  Occasionally 
longitudinal  striae  are  to  be  detected  in  muscular  fibre 
instead  of  the  transverse  stripes,  and  in  rare  instances 
both  the  longitudinal  and  transverse  stripes  are  pre- 
sent. (PL  X.  fig.  II.  4,  5.)  If  this  contained  sub- 
stance is  still  farther  analysed  by  the  aid  of  chemical 
re-agents  (chromic  acid,  alcohol,  etc.)  or  prepared  by 
boiling,  and  even  sometimes  without  the  employment 

*  This  term  was  introduced  by  Bowman,  who  first  investigated  and     ,    . 
described  the  sarcolemma,  and  its  relation  to  the  primitive  muscular  fibre 
of  the  striated  variety.    V.  Cyclop,  of  Anat.  and  Physiology,  Art.  Muscle, 
and  Todd  and  Bowman's  Phyt*  Anat.— (Ed.} 


50  MUSCLES. 

of  these  artificial  means,  it  becomes  evident  that  it  is 
composed  of  two  distinct  constituents — one  granular 
and  the  other  amorphous,  the  latter  being  very  vari- 
able in  amount,  and  serving  as  a  connecting  medium 
to  the  former — which  is  thus  imbedded  in  it.  (PL  IX. 
fig.  V.  5.)  These  minute  granules — the  sar cents  ele- 
ments of  Bowman  (PL  X.  fig.  II.  5),  are  slightly  flat- 
tened in  the  direction  of  the  length  and  breadth  of 
the  fibre,  and  measure,  on  an  average,  nnr  <rth  of  a  line. 
These  little  bodies  seem  to  be  the  active  agents  in  the 
production  of  the  contractility  of  muscle ;  it  is  in 
them,  and  in  their  relation  to  the  amorphous  material 
by  which  they  are  enveloped,  that  we  are  to  look  for 
the  power  which  the  muscular  fibre  possesses  of 
changing  its  size  and  shape. 

In  fact,  according  as  these  ultimate  corpuscles 
approach  each  other  more  closely  in  the  direction  of 
the  length  of  the  fibre  than  in  the  direction  of  its 
breadth,  it  will  assume  the  fibrillated  appearance 
(PL  X.  fig.  II.  4,  5),  or,  in  the  opposite  case,  the 
appearance  of  discs  piled  upon  one  another.  This 
latter  disposition  of  the  sarcous  elements  presents  a 
more  striking  appearance,  when  between  the  discs 
which  result  from  their  arrangement  in  transverse 
rows,  a  large  amount  of  the  amorphous  hyaline  sub- 
stance is  present,  as  in  fig.  V.  (PL  IX.  5). 

To  sum  up  in  a  word  :  the  ultimate  fibre  of  striped 
muscular  tissue  is  composed  of  an  external  envelope 
of  simple  structureless  membrane,  which  contains  a 
granular  material  of  soft  consistence ;  and  the  varia- 
tions in  appearance  of  the  striae  by  which  it  is  marked, 
are  due  to  the  varying  relations  which  these  granules 
are  capable  of  assuming  to  each  other, 


MUSCLES.  51 


1  he  striped  muscular  fibre  is  continuous  throughout 
its  whole  length,  and  this  corresponds  accurately  with  tongue' 
that  of  the  fasciculus,  or  bundle,  of  which  it  forms  a 
constituent  part.  Up  to  the  present  time  we  know 
of  but  two  organs  which  constitute  exceptions  to  this 
law,  and  these  are  the  heart  and  the  tongue.  The 
muscular  fibres  of  the  heart  are  branched,  and  form 
very  frequent  anastomoses,  recalling  the  disposition 
of  the  columnce  carnece  of  the  ventricles,  and  explain- 
ing the  admirable  correspondence  and  unity  of  action 
in  the  movements  of  the  organ  (PL  X.  fig.  III).  The 
fibres  of  the  tongue  give  off  branches  only  in  its  sub- 
mucous  layer  of  muscular  tissue,  and  these  do  not 
appear  to  anastomose.  They  terminate  by  pointed 
extremities  which  are  attached  to  minute  fasciculi  of 
connective  fibres,  which  seem  to  act  as  their  tendons 
—  at  least  this  is  the  opinion  of  most  authorities. 
The  ultimate  fibres  of  striped  muscle  are  united 
together  by  delicate  lamellae  of  connecting  tissue 
(perymisium),  and  thus  constitute  secondary  fasciculi. 
These  again,  surrounded  by  sheaths  of  the  same 
material,  but  somewhat  more  dense,  form  tertiary 
fasciculi  ;  and,  finally,  the  entire  muscle  is  enveloped 
by  a  still  stouter  sheath  which  forms  its  external 
perymisium.  In  this  outer  membrane  we  find  the 
ramifications  of  the  nerves  and  nutritious  vessels  of 
the  muscle. 

The  striated  fibre  terminates  by  a  rounded  extre-  Termination  of 

J  striated  fibres. 

mity,  which  is  simply  in  close  apposition  with  its 
tendon.  Nevertheless  Kolliker  asserts  that  this 
arrangement,  which  is  certainly  the  most  common  of 
all,  is  found  to  exist  only  where  the  muscular  fibre 


52  MUSCLES. 

meets  its  tendon  obliquely ;  but  where  it  is  conti- 
nuous, in  the  same  line  with  the  tendinous  fasciculus 
with  which  it  corresponds,  the  two  tissues  blend 
together  insensibly,  without  any  line  of  demarcation 
at  their  point  of  contact.* 
Aspect  of  the  We  cannot  close  our  description  of  muscular  fibre 

striated  fibre  dur- 

antraction.  wjt}lout  remarking  that  Weberf  long  since  demon- 
strated that  it  does  not  wrinkle  during  contraction. 
It  becomes  shorter  by  increasing  in  breadth  and 
thickness,  at  the  same  time,  just  like  a  cylinder  of 
caoutchouc  after  being  stretched.  The  zigzag  wrin- 
kling occurs  only  where  the  extremities  of  the  fibre,  as 
it  shortens,  do  not  return  by  the  same  line  in  which 
it  was  elongated.  It  is  very  easy  to  verify  the  exact- 
ness of  Weber's  assertion  by  examining,  under  the 
microscope,  the  glosso-laryngeal  muscle  of  the  frog, 
when  under  the  influence  of  galvanic  stimulus. 
Nerves  of  mus-  T}ie  nerves  of  striped  muscle  are  supplied  both  by 
the  cerebro-spinal  axis,  and  the  sympathetic  system  ; 
but  those  derived  from  the  latter  source  are  very  few 
in  number. 

'"  "  In  the  human  body  the  smooth  muscular  tissue  nowhere  forms  large 
isolated  muscles,  as  in  the  case  of  the  recto-penal  muscles  of  mammals, 
for  example,  but  occurs  either  scattered  in  the  connective  tissue,  or  in 
the  form  of  muscular  membranes.  In  both  cases  its  bundles  are  either 
arranged  parallel  to  each  other,  or  united  to  form  networks ;  and,  even 
in  man,  are  connected  in  many  places  with  tendons  of  elastic  tissue,  as 
first  detected  by  me  in  the  tracheal  muscles,  and  in  the  cutaneous  feather 
muscles  of  birds."  Kolliker,  Manual  of  Human  Microscopic  Anat. 
London,  1860,  p.  65.— (Ed.) 

t  This  is  not  the  celebrated  Weber,  Professor  of  Anatomy  at  Leipzig, 
and  famous  for  his  researches  on  the  structure  of  the  placenta,  the  ske- 
leton, joints,  etc.,  but  E.  Weber,  author  of  an  elaborate  article,  "  Muskel- 
bewegung,"  in  Wagner's  Handworterbucb,  1846. — (Ed.)* 


MUSCLES.  53 

As  they  enter  the  substance  of  a  muscle,  its  nerves 
are  united  in  bundles,  and  pursue  a  course  almost  at 
right  angles  to  its  fibres.  Very  soon  they  divide  and 
subdivide,  gradually  approaching  the  same  direction 
as  the  fibres  of  the  muscle,  and  finally  the  smaller 
branches  run  almost  parallel  with  them  (PL  XI).  In 
their  course,  the  nervous  filaments  separate  sometimes 
from  each  other  without  anastomosing;  and,  again, 
they  unite  after  separating,  in  such  a  manner  as  to 
form  loops,  and  even  many  series  of  loops,  or  a  net- 
work of  anastomoses. 

As  to  the  mode  in  which  nervous  filaments  ter- 
minate in  muscle,  the  following  is  the  result  of  our 
examination  of  different  muscles  of  the  frog.  At  the 
points  where  the  little  bundles  of  nerves  separate, 
the  majority  of  their  primitive  fibres  present  a  dis- 
tinct contraction  in  diameter,  a  strangulation,  to  half 
their  previous  size.  From  these  contractions  two 
branches  usually,  sometimes  three,  take  their  origin ; 
and  these,  after  running  a  short  distance,  undergo  a 
similar  contraction  and  branching.  Finally,  the  ter- 
minal fibres  taper  off  quite  rapidly,  soon  show  but  a 
single  outline,  and  at  last  seem  to  lose  themselves  on 
the  sarcolemma  (PL  XIV.  fig.  I). 

Can  we  infer  from  these  facts  a  similar  distribution 
of  the  nerves  of  striated  muscle  in  man  ?  From  the 
researches  of  Valentin,*  confirmed  in  part  by  Kol- 
liker,  it  would  seem  not.  Both  of  these  authorities 
assert  that  they  have  seen  nervous  fibres  terminating 

*  G.  Valentin,  Professor  of  Anatomy  and  Physiology  in  the  Uni- 
versity of  Berne,  author  of  the  treatise  on  "  Nemologie1'1  in  the  Encyclo- 
pedie  Anatomique,  Lehrbuch  der  Physiologic,  etc.,  etc.«-~(.E$.) 


54  MUSCLES. 

by  loops,  in  the  muscles  of  the  smaller  mammiferse, 
and  in  man.  Lebert*  also  has  given  a  representation 
of  nerves  terminating  by  loops,  in  the  muscles  of  the 
abdomen,  and  in  the  tongue  of  the  frog. 

Remak  has  discovered  microscopical  nervous  gan- 
glia in  the  auriculo-ventricular  septa  of  the  frog's  heart, 
and  very  rightly  ascribes  to  their  influence  the  persist- 
ence of  the  rhythmical  pulsations  of  the  organ,  when 
isolated  from  the  body,  as  well  as  the  continued  regu- 
lar contractions  in  the  septum  itself,  when  this  has 
been  detached  from  the  rest  of  the  heart. 

From  the  observations  of  Reichert,  who  has  care- 
fully studied  the  distribution  of  the  nerves  of  the 
frog's  heart,  it  would  appear  that  each  muscular  fibre 
is  in  relation  with  several  nervous  filaments.  Volk- 
man  has  sought  to  establish  the  numerical  proportion 
of  large  and  slender  fibres  which  enter  the  substance 
of  a  striped  muscle ;  he  has  counted  twelve  slender 
fibres  in  an  hundred. 

Very  little  is  known  of  the  mode  of  distribution  of 
its  nerves  to  the  non-striated  muscular  tissue.  It  may 
be  asserted,  probably,  with  truth,  that  it  is  much  less 
richly  supplied  with  nerves  than  the  striated  variety ; 
the  middle  coat  of  the  arteries  affords  evidence  of 
this. 


*  H.  Lebert,  at  present  Professor  of  Clinical  Medicine  in  the  University 

of  Breslau,  author  of  Physiologic  pathologique,  2  vols.  Paris,  1845  ;  thje 

"  Traite  &  Anatomic  pathologique"  now  in  course  of  publication,  and 

numerous  papers  in  the  Annales  des  Sciences  Naturelles,  and  elsewhere. 


t  Bogislav  Keichert,  Professor   of  Anatomy  at  Berlin,  successor  to 
Muller.—  (Ed.) 
k    t  Professor  of  Anatomy  at  Dorpat,  Livonia.—  (Ed.) 


MUSCLES.  55 

Of  tke  diverse  theories  put  forth  as  to  the  mode  of 
development  of  muscular  tissue,  we  shall  notice  only 
that  which  seems  to  us  most  in  conformity  with  ascer- 
tained facts. 

Muscular  tissue  is  derived  originally,  like  all  the 
other  tissues,  from  the  primordial  cells  of  the  embryo, 
which,  at  first,  everywhere  the  same,  undergo  a  spe- 
cial metamorphosis  in  order  to  form  each  and  every 
histological  element. 

The  embryonic  cells  which  are  about  to  form  mus- 
cular fibres  at  first  increase  in  length,  and  then, 
coming  in  contact  with  each  other  by  their  narrowing 
extremities,  finish  by  uniting  together.  Afterwards, 
the  partitions  formed  by  these  lines  of  union  disap- 
pear, and  we  have,  as  a  result  of  the  process,  tubes 
of  structureless  membrane  presenting  constrictions 
(which  mark  the  line  of  fusion  of  the  original  cells), 
and  intervening  expansions,  each  of  which  contains  a 
nucleus  (PL  IX.  fig.  IV.  1,  2,  3).  At  this  period 
their  diameter  varies  from  ToVoth  to  4¥<rth  of  a  line. 
During  the  process  of  transformation  the  contents  of 
the  cells,  at  first  hyaline,  become  granular,  and  the 
granules,  which  bear  some  resemblance  to  oil-globules, 
assume  a  regular  arrangement  either  in  longitudinal  or 
transverse  rows  (PL  IX.  fig.  IV.  4,  5,  6).  Still  later, 
the  muscular  fibre,  thus  formed,  increases  in  thick 
ness,  assumes  a  cylindrical  shape,  and  its  several  cha- 
racteristic features  become  more  and  more  obvious ; 
the  division  of  its  interior  into  fibrillse  is  noticed,  and 
also  the  appearance  of  a  large  quantity  of  nuclei,  which 
take  their  origin  by  endogenous  multiplication.  If,  at 
this  moment,  the  extremity  of  a  fibre  is  examined  on 


56  MUSCLES. 

transverse  section,  it  is  found  that  the  changes  just 
described  take  place  from  its  circumference  towards 
its  centre,  very  rarely  in  the  opposite  direction.  Fi- 
nally, the  fibrillse  increase  in  number,  whilst  their 
newly  formed  nuclei  are  absorbed,  and  the  mus- 
cular fibre  gradually  puts  on  its  permanent  appear- 
ance. 

The  following  is  a  summary,  in  two  words,  of  this 
process — which  seems  best  borne  out  by  facts :  fusion 
of  embryonic  cells,  T\  hich  by  their  union  form  a  tube, 
or  myolemma;  metamorphosis  of  its  contents  into 
elementary  granules,  and  their  subsequent  develop- 
ment into  fibrillse  or  discs. 

During  the  earlier  periods  of  development  and 
growth  of  the  fibres  of  muscle,  they  are  enveloped  by 
a  large  number  of  elementary  cells — some  oval  in 
shape,  others  smaller  and  round.  Of  these,  the 
greater  proportion  are  destined  to  form  the  connect- 
ing tissue  and  other  parts  which  constitute  a  com- 
plete muscle  ;  and  the  rest,  after  having  contributed, 
no  doubt,  to  the  growth  of  the  persistent  elements  of 
the  tissue,  fade  and  disappear.  The  muscular  fibres 
of  the  heart  are  developed  in  accordance  with  the 
same  rules,  with  this  exception,  that,  in  place  of  the 
fusion  and  subsequent  transformation  of  simple  cells, 
these  phenomena  are  accomplished  by  means  of 
branching,  or  star-shaped  cells ;  hence  arises  the 
branching  character  of  the  fibres  of  this  organ.  The 
fibres  of  muscle,  having  attained  their  complete 
development,  remain  permanently,  for  an  indefinite 
period,  in  this  state,  and  the  metamorphoses  which 
occasionally  occur  in  their  interior,  are  marked 


MUSCLES.  57 

by  a  very  feeble  amount  of  vital  activity.  Up  to 
the  present  time  the  mode  in  which  muscular  fibre 
is  reproduced,  has  not  been  satisfactorily  made 
out* 

*  Wounds  of  muscles  never  heal  by  means  of  transversely  striated  mus- 
cular substance;  .  .  .  they  heal  simply  by  means  of  a  tendinous 
cicatrix.  An  instance  of  new  formation  of  muscular  tissue  has  been  seen 
by  Rokitansky  in  a  tumor  of  the  testicle  of  an  individual  eighteen  years 
old  ;  and  another  by  Virchow,  in  an  ovarian  tumor.  Kolliker,  op.  cit. 


CHAPTER  V. 

Elements  of  Nervous    Tissue. 

THE  analysis  of  nervous  tissue  reduces  its  anato- 
mical elements  to  two  forms, ^iz.  the  fibre,  and  the 
cell. 

ne™etflSe.of  The  fibres  of  nerve  tissue  present  variations  in  the 
details  of  their  structure;  sometimes  consisting  of  a 
tube  of  a  certain  diameter,  with  envelope  and  con- 
tents perfectly  distinct ;  whilst,  at  others,  on  the  con- 
trary, the  envelope  and  its  contents  so  blend  together 
as  to  constitute  a  simple  homogeneous  fibre. 

The  envelope  of  the  nerve  tube  is  entirely  struc- 
tureless, and  possessed  of  a  certain  amount  of  elas- 
ticity. Immediately  in  contact  with  its  internal  sur- 
face we  find  a  soft  amorphous  substance  of  an  albumi- 
nous and  fatty  nature — this  is  the  nervous  marrow, 
or  medullary  sheath.  In  fresh  nerve  fibres  this  me- 
dulla is  homogeneous,  and  constitutes  a  regular  tube  ; 
but  soon  after  death  it  becomes  disintegrated,  and 
separates  itself  into  lumpy  masses,  between  and  upon 
which  the  envelope  contracts  so  as  to  give  the  fibre  a 
varicose  appearance  (PL  XII.  fig.  I.).  Finally,  the 
central  axis  of  the  tube  is  occupied  by  a  cylinder  of 
amorphous  material,  of  an  albuminous  nature,  more 
compact  and  more  tenacious  than  the  medulla,  which 
is  known  by  the  name  of  axis-cylinder  (PL  XII.  fig. 
I.  7).  It  is  exceedingly  difficult  to  make  out  the  axis- 


ELEMENTS    OF    NERVOUS    TISSUE.  59 

cylinder  in  fresh  nerve  tissue  ;  but  occasionally  it*can 
be  detected  protruding  from  the  broken  extremity  of 
a  nerve  tube.  In  order  to  render  it  more  distinct,  a 
number  of  chemical  reagents  are  employed  ;  amongst 
these,  dilute  chromic  acid  seems  to  be  the  most  effi- 
cacious. In  nerves  still  alive,  so  to  speak,  those,  for 
example,  of  a  specimen  of  muscle  still  capable  of  con- 
traction— we  can  distinguish  only  the  envelope  of  the 
tube  with  uniform  <?r  homogeneous  contents;  the 
axis-cylinder  is  not  recognizable — hence  it  has  been 
regarded  as  -the  result  of  post-mortem,  or  artificial 
change. 

To  repeat :  in  a  nerve  tube  we  observe,  first,  two 
outer  parallel  lines  representing  the  enveloping  mem- 
brane ;  then,  within  these,  two  other  parallel  lines, 
which  mark  the  limits  of  the  medulla;  and  finally,  in 
its  centre,  two  more  lines,  always  parallel,  which 
form  the  outlines  of  the  axis-cylinder,  when  it  is  visi- 
ble (PI.  XII.  fig.  I.  5,  6,  7).  The  diameter  of  these 
tubes  varies  from  rsad  to  26-6-th  of  a  line. 

There  are  other  fibres,  smaller  than  those  just  Fine  nerve  fibres. 
described,  in  which  but  two  parallel  lines  on  each 
side  of  the  tube  can  be  made  out — one  of  which  cor- 
responds to  the  envelope,  and  the  other  to  its  con- 
tents. The  most  minute  fibres  of  all  (Wo  o-th  to  TTO  o-th 
of  a  line)  are  simple  solid  cylinders,  limited  by  two 
exterior  lines  only,  in  which  it  is  impossible  to  dis- 
tinguish the  envelope  from  the  material  contained 
within  it.  In  the  first  of  these  it  has  been  supposed 
that  the  medulla  was  absent — the  envelope  and  axis- 
cylinder  alone  remaining,  and  that  the  latter,  or  most 
minute  of  all,  was  formed  by  the  axis-cylinder  alone. 


60  ELEMENTS    OF    NERVOUS    TISSUE. 

This,  however,  is  not,  as  yet,  susceptible  of  demon- 
stration. Nerve  fibres  remain"  entire  whilst  in  the 
nervous  centres,  and  throughout  their  whole  course ; 
but,  at  their  peripheral  extremities,  most  of  them 
divide  into  branches.  This  fact  is  perfectly  made  out 
as  far  as  the  nerves  of  motion  are  concerned,  as  we 
have  already  seen  whilst  studying  the  structure  of 
striped  muscle.  It  is  probably  true  also  of  the  nerves 
of  mucous  membranes,  and  of  the  external  integu- 
ment. 

Their  mode  of  termination,  which  has  been  a  sub- 
ject of  research  for  so  many  minute  anatomists,  is  not 
yet  definitely  established  for  all  the  tissues.  It  ap- 
pears to  be  susceptible  of  demonstration  that  in  the 
ganglia,  and  other  nervous  centres,  nerve  fibres  are  in 
contact  with  nerve  cells.  It  is  equally  beyond  doubt 
that  in  the  muscles,  and  in  certain  regions  of  the  skin 
and  mucous  membranes,  nerve  fibres,  after  undergoing 
division,  terminate  by  free  extremities  (as  in  muscle), 
and  sometimes  by  again  anastomosing  with  each  other 
(as  in  the  skin  and  mucous  membrane  of  the  tongue). 
The  experiments  of  Prof.  Cl.  Bernard,  on  the  phe- 
nomena of  recurrent  sensibility,  tend  to  prove  that  a 
large  proportion  of  sensitive  fibres  end  by  forming 
loops.  We  shall  see  hereafter  that  in  the  eye,  the 
ear,  and  the  olfactory  mucous  membrane,  they  termi- 
nate by  contact  with  nerve  cells,  as  in  the  nervous 
centres.  Finally,  in  the  integument  of  the  palm  of 
the  hand  and  sole  of  the  foot,  we  find,  in  fibres  of 
sensation,  two  peculiar  modes  of  termination,  viz.  the 
corpuscles  of  Pacini  and  corpuscles  of  Meissner,  which 
we  are  about  to  describe. 


ELEMENTS    OF   NERVOUS    TISSUE.  61 

The  corpuscles  of  Pacini*  are  little  ovoid,  <  r  rather 
ellipsoid  bodies,  attached  by  one  extremity,  by  means 
of  a  very  delicate  pedicle,  to  the  nerves  of  the  fingers 
and  toes.  They  consist  of  a  central  cavity  inclosing 
the  extremity  of  a  nerve  fibre,  and  an  external  enve- 
lope. This  latter  resembles  the  cornea  in  its  struc- 
ture ;  it  is  made  up  of  a  number  of  amorphous 
lamellae,  overlay  ing  each  other  concentrically,  between 
which  we  find  a  great  number  of  plasmatic  nuclei 
disposed  in  regular  series  (PL  XIV.  fig.  II.  2).  The 
more  superficial  lamellae  lose  themselves  on  the  sur- 
face of  the  pedicle.  The  central  cavity  is  filled  with 
a  fine  granular  substance,  in  which  the  outlines  of 
very  pale  cells  can  sometimes  be  distinguished.  Fi- 
nally, in  the  central  axis  of  the  cavity  is  a  nerve 
fibre,  which  is  remarkably  pale,  and,  for  this  reason, 
not  easy  to  discover.  By  tracing  it  onward  it  is  seen 
to  terminate  in  a  slight  bulb  (PL  XIV.  fig.  II.  4), 
whilst  below,  it  is  found  occupying  the  centre  of  the 
pedicle,  through  which  it  is  continuous  with  the  ner- 
vous twig  on  which  the  Pacinian  corpuscle  is  situated. 
Some  authors  have  represented  the  nervous  filament 
as  dividing,  in  the  interior  of  the  cavity  of  the  cor- 
puscle, into  two  or  three  terminal  branches. 

Pacinian  corpuscles  are  found  also  in  other  loca- 
lities than  in  connexion  with  the  nerves  of  the 
fingers  and  toes.  Kolliker  has  met  with  them  in 
connexion  with  the  cutaneous  nerves  of  the  arm  and 
forearm,  on  the  back  of  the  hand  and  foot,  and  in 
the  terminal  branches  of  the  internal  pudic,  inter- 

*  Nuovi  organ!  scoperti  nel  corpo  umano  del  Dottore  Filippo  Pacini, 
Pistoja,  1840.— (Ed.} 


62  ELEMENTS   OF   NERVOUS   TISSUE. 

costal,  and  sacral  nerves,  and,  finally,  in  the  great  sym- 
pathetic plexus  which  surrounds  the  abdominal  aorta. 
°f  The  corPusc^e  °f  Meissner,*  or  tactile  corpuscle,  is  a 
minute  microscopical  organ  which  occupies  the  inte- 
rior of  some  of  the  papillae  of  the  true  skin.  To  get 
a  view  of  them,  it  is  necessary  to  make  very  delicate 
sections  of  the  skin  of  the  palmar  surface  of  the  last 
phalanges  of  the  fingers  or  toes,  and  to  apply  dilute 
acetic  acid  to  the  section  under  the  microscope.  Its 
shape,  like  that  of  the  Pacinian  corpuscle,  resembles 
an  ellipse  (PL  XXIII.  fig.  II.  6).  Its  structure  con- 
sists of  a  faintly  striated  substance  studded  with  plas- 
matic  nuclei  (fig.  II.  9)  arranged  transversely.  At 
the  inferior,  or  attached  extremity  of  the  corpuscle,  a 
nervous  filament  is  seen  applying  itself  to  its  surface, 
in  the  inequalities  of  which  it  seems  to  lose  itself  by 
describing  tortuous  curves  which  are  only  occasionally 
visible.  Whether  it  ends  by  becoming  continuous  with 
the  substance  of  the  corpuscle,  or  by  simple  division, 
or  by  forming  a  loop,  has  not  as  yet  been  made  out. 
Kolliker  has  found  these  tactile  corpuscles  in  the 
papillae  of  the  vermilion  borders  of  the  lips,  in  the 
fungiform  papillae  of  the  point  of  the  tongue,  on  the 
nipple,  the  glans  penis  and  clitoris ;  but  they  are 
encountered  in  greatest  number  in  the  skin  covering 
the  last  row  of  phalanges  of  the  fingers  and  toes. 
Nervous  ceiiu.  Nerve  cells,  or  corpuscles,  vary  exceedingly  both  in 
size  and  shape.  In  all  of  their  forms  they  present, 
however,  every  element  of  a  perfect  cell.  Thus  they 
have  a  very  delicate  cell-wall,  so  thin  and  delicate,  in 

*  Successor  to  Rudolf  Wagner  in  the  chair   of  Physiology  at  Got- 
tingen.— (Ed.) 


ELEMENTS    OF   NERVOUS   TISSUE.  63 

fact,  as  to  have  led  some  to  doubt  its  existence. 
They  contain  a  pale,  finely  granular  substance,  toge- 
ther with  a  variable  amount  of  pigment,  as  a  general 
rule  (PL  XIII.  fig.  I.  6).  The  nucleus  is  spherical  in 
shape,  and  much  more  distinctly  marked  in  its  out- 
line than  the  cell  itself,  and  amongst  the  granules 
which  it  contains  the  nucleolus  is  readily  distin- 
guished by  an  unusual  degree  of  brilliancy.  In  the 
ganglia  there  are  some  cells  which,  outside  of  their 
own  proper  cell-wall,  are  enveloped  by  another,  a 
second  and  much  thicker  envelope,  consisting  of 
structureless  or  very  delicately  fibrillated  material, 
full  of  oval  nuclei  (PL  XIII.  fig.  I.  8).  This  seems 
to  be  partially  developed  connecting  tissue  belonging 
to  the  proper  stroma  of  the  organ. 

In  regard  to  their  form,  nerve  cells  are  either  ^ape  of  nerve 
simply  spherical,  or  furnished  with  one,  two,  three 
or  more,  tubular  prolongations  of  their  cell  walls  (PL 
XII.  fig.  VI. ;  PL  Xllirfig.  I).  The  spherical  cells 
seem  to  be  merely  in  contact  with  the  neighboring 
nervous  elements  amongst  which  they  are  situated ; 
but  the  multipolar  or  caudate  cells  are  continuous, 
by  their  prolongations,  with  nerve  fibres,  or  their 
caudate  processes  anastomose  with  each  other,  as  can 
be  readily  seen  in  the  grey  matter  of  the  cerebellum. 

Nerve  cells,  associated  with  other  elements,  are  Distribution, 
found  in  the  grey  matter  of  the  cerebro-spinal  axis, 
and  in  the  ganglia  of  the  cerebro-spinal  nerves  and 
those  of  the  great  sympathetic.  They  are  also  found 
in  the  nerves  which  traverse  the  substance  of  organs, 
in  which  they  form  microscopic  ganglia.  Finally,  as 
we  have  already  intimated,  the  nervous  fibres  of  the 


64  ELEMENTS    OF   NERVOUS    TISSUE, 

retina  terminate  in  globular  masses,  and  likewise 
those  of  the  internal  ear,  and  olfactory  mucous  mem- 
brane. 

of  Nerves,  whether  in  main  trunks  or  branches,  are 
bundles,  consisting  of  nerve  fibres  in  variable  number ; 
these  are  grouped  together  in  primitive  and  secon- 
dary fasciculi.  The  primitive  fasciculi  consist  of  a 
few  fibres  surrounded  by  delicate  connecting  tissue, 
faintly  fibrillated  and  studded  with  plasmatic  cells ; 
this  is  called  the  neurilemma,  from  its  analogy  with 
the  myolemma  of  striated  muscular  fibre  (Robin*). 
Secondary  fasciculi  are  made  up  of  primary  bundles, 
which  are  held  together  by  a  much  denser  membrane 
consisting  of  ordinary  connecting  tissue. 

In  large  nervous  trunks,  fibres  of  every  size  are 
found  ;  but  those  of  largest  size  are  most  abundant  in 
the  anterior  roots  of  the  spinal  nerves,  and  in  nerves 
of  motion,  whilst  fine  fibres  are  found  in  greater 
numbers  in  their  posterior  roots,  in  nerves  of  sen- 
sation, and  in  branches  of  the  great  sympathetic. 
These  latter  also  contain  a  certain  proportion  of  flat, 
pale,  smooth,  or  faintly, striated  fibres,  provided  with 
well  marked  oval  nuclei,  and  known  as  the  fibres  of 
Remak  (PI.  XII.  fig.  II.) .  It  is  not  as  yet  fully  deter- 
mined whether  these  are  really  nerve  fibres,  as 
Rernak  asserts,  or  merely  a  peculiar  form  of  connect- 
ing tissue,  as  Kolliker  and  some  others  are  disposed 
to  think.  We  hold  to  the  latter  opinion,  and  regard 
the  fibres  of  Reinak  as  prolongations  of  the  nucleated 
connecting  tissue  which  forms  the  stroma  of  the  ner- 

*  Charles  Kobin,  Prof,  agrege  d'histoire  naturelle  medicale  a  la  Faculte 
de  Medecine  de  Paris,  Prof,  d' Anatomic  generate,  etc.,  etc. — (Ed.} 


ELEMENTS    OF    NERVOUS    TISSUE.  65 

vous  ganglia  (PL  XIII.  fig.  III.).  The  nerves  are  not 
very  rich  in  blood-vessels ;  they  form  a  net-work  of 
large  meshes,  the  terminal  branches  from  which  ra- 
mify in  the  neurileinrna ;  they  do  not  come  directly 
in  contact  with  the  naked  primitive  fibre  (Kolliker). 

In  addition  to  the  nerve  cells,  which  constitute 
their  most  important  element,  nervous  ganglia  con- 
sist of  an  intermingling  of  very  delicate  connective 
fibres  with  oval  nuclei,  and  a  large  number  of  blood- 
vessels (PI.  XIII.  fig.  III.).  The  connective  element 
is  the  same  which  has  been  already  mentioned  as 
forming  the  thick  nucleated  external  or  second  enve- 
lope of  certain  nerve  cells,  and  the  sympathetic  nerve 
fibres  of  Remak  are  also  derived  from  it,  for  their 
constituent  elements  are  identical  in  form,  and  be- 
have similarly  under  the  influence  of  chemical 
reagents. 

It  is  generally  conceded  that  nervous  ganglia  con- 
tain all  of  the  different  forms  of  nerve  cells.  In  those 
of  the  spinal  nerves,  cells  with  two  branches  (bicau- 
date)  are  most  numerous,  and  of  these  there  are  two 
kinds.  The  one  have  their  prolongations  given  off 
from  diametrically  opposite  points  of  their  circum- 
ference, one  being  continuous  with  a  nerve  fibre  from 
the  spinal  marrow,  and  the  other  with  a  peripheral 
nerve  (PL  XII.  fig.  III.).  The  other  kind  of  bi-cau- 
date  cells  give  off  both  of  their  prolongations  in  the 
same  direction,  and  always  towards  the  surface. 
Finally,  the  cells  with  but  one  prolongation  (uni- 
polar) are  always  continuous  with  a  peripheral  fibre. 
In  the  ganglia  of  the  sympathetic  system  most  of  the 
multi  polar  nerve  cells  seem  to  send  off  the  same 


66  ELEMENTS    OF   NERVOUS   TISSUE. 

4 

number  of  processes,  according  to  Leydig,  as  there  are 
nerves  connected  with  the  ganglion  (PL  XII.  fig. 
IV.).  The  study  of  the  relations  which  exist  between 
nerve  cells  and  nerve  fibres  is  one  of  difficulty ;  very 
thin  sections  must  be  made  of  fresh  specimens  of 
ganglia,  and  treated  with  dilute  acetic  acid,  or  caustic 
potassa,  or  still  better,  perhaps,  by  a  solution  of  car- 
mine in  liquid  ammonia,  as  recommended  by  Jacu- 
bowitsch.*  Similar  sections  may  be  made  of  ganglia 
hardened  in  chromic  acid ;  and  very  minute  speci- 
mens of  ganglia  are  sometimes  immersed  in  potash 
and  moderately  compressed  between  two  slips  of 
glass. 

Nervous  centres.       The  arrangement  of  the  elements  of  nerve-tissue, 

throughout   the   cerebro-spinal  centres,  is  far  from 

spinal  marrow,  being  clearly  made  out.     The  spinal  cord  consists  of 

a  central  mass  of  grey  matter,  surrounded  on  all  sides 

by  white   matter.     The   latter   is  made   up  almost 

wwte  substance-  exclusively  of  nerve  fibres,  with  some  blood-vessels, 
supported  by  scanty  and  delicate  connecting  tissue. 
By  the  aid  of  transverse  and  longitudinal  sections, 
we  can  see  that  some  of  the  nerve  fibres  run  parallel 
with,  and  others  perpendicular  to,  the  axis  of  the 
cord.  The  former  constitute  the  greater  proportion 
of  the  white  substance,  and  are  found  everywhere  ; 
whilst  the  latter  are  only  to  be  seen  where  the  roots 
of  the  spinal  nerves  become  continuous  with  the  sub- 
stance of  the  cord.  It  is  to  be  noted  also  that  the 


*  Jacubowitsch  and  Owsjannikow  are  connected  with  one  of  the  Russian 
Universities,  and  published  their  researches  on  the  nerves  in  the  Bull,  de 
1'Acad.  de  Petersbourg,  classe  k  phys.-^Mathem.,  torn.  xiv.  No.  323, 
page  173.— (Ed.) 


ELEMENTS    OF   NERVOUS   TISSUE.  67 

nerve  fibres  of  the  spinal  cord  are  of  the  smaller 
varieties. 

The  grey  matter  of  the  cord  forms  a  quadrangular  Grey  matter, 
prism  with  hollowed  sides,  or  rather,  a  fluted  column. 
In  its  centre  is  a  canal,  sometimes  closed  in  the  adult, 
and  of  greater  diameter  at  either  extremity  of  the 
cord,  than  in  its  middle.  Its  walls  are  formed  by  a 
layer  of  connecting  tissue  of  varied  thickness,  rich  in 
plasm atic  cells,  and  lined  internally  by  a  stratum  of 
cylindrical  ciliated  epithelium.  Virchow,  Kolliker, 
and  Ley  dig*  have  particularly  directed  the  attention 
of  microscopists  to  this  cylinder  of  connecting  tissue 
which  is  thus  inclosed  in  the  grey  matter  of  the  cord, 
as  the  plasmatic  cells  which  it  contains  are  often  the 
origin  of  morbid  formations  which  occasionally  in- 
volve its  substance. 

The  grey  matter  itself  is  made  up  of  blood-vessels.  Eeiation  be- 

17  .  *•  1    tween  nerve  cells 

fine  nerve  fibres,  and  caudate  nerve  cells,  the  largest  of  ™rddfbreB' in  the 
which  are  found  towards  the  extremities  of  the  ante- 
rior horns.  In  man  the  connexions  of  the  caudate 
cells  have  not  as  yet  been  clearly  demonstrated. 
This  is  not  true,  however,  of  some  of  the  lower  ani- 
mals ;  thus,  in  accordance  with  the  researches  of 
Owsjannikow,  in  fishes,  each  cell  has  five  prolonga- 
tions, which  are  disposed  as  follows:  The  most  internal 
process,  after  it  leaves  the  cell,  enters  the  white  com- 
missure of  the  cord,  and  traversing  it,  reaches  the 
white  substance  of  the  opposite  side,  where  it  loses 
itself  in  another  similar  cell  (PL  XII.  fig.  V.  7)  ;  this 
is  the  branch  which  establishes  a  route  of  connexion 

Professor  of  Comparative  Anatomy  in  the  University  of  Wiirzburg. 


68  ELEMENTS    OF    NERVOUS    TISSUE. 


between  the  two  lateral  masses  of  nerve  cells  of 
either  side.  The  anterior  process  runs  into  the  ante- 
rior, and  the  posterior,  into  the  posterior  root,  of  each 
spinal  nerve;  and  finally,  the  processes  given  off 
above  and  below  become  continuous  with  the  longi- 
tudinal fibres  of  the  cord  (PL  XII.  fig.  V.).  It 
remains  now  to  be  proved,  whether  or  no  a  similar 
disposition  exists  in  the  mammalia  and  in  man. 
in  the  encepha.  The  facts  ascertained  in  relation  to  the  minute 

Ion. 

structure  of  the  nervous  tissue  of  the  encephalon,  are 
still  more  incomplete.  Here,  as  in  the  spinal  marrow, 
there  is  a  white  substance  possessing  very  little  vas- 
cularity,  and  composed  entirely  of  nerve  fibres,  and  a 
grey  matter  consisting  of  vesicular  elements  mingled 
with  nerve  fibres,  and  very  numerous  blood-capil- 
laries. Besides  the  multipolar  or  caudate  cells,  whose 
processes  anastomose  with  each  other,  and  become 
continuous  with  nerve  fibres,  there  exist  large  num- 
bers of  nuclei  and  spherical  cells — especially  in  those 
portions  of  the  grey  matter  of  the  brain  and  cere- 
bellum which  lie  nearest  the  surface  (PL  XIII.  fig. 
II.).  What  is  the  nature  and  uses  of  these  nuclei  ? 
Are  they  germs  of  future  nerve  cells,  or  are  they 
only  the  analogues  of  the  oval  nuclei  which  we  found 
mingled  with  the  connective  fibres  of  the  ganglia  ? 
These  are  questions  which  remain  to  be  answered. 
As  for  the  arrangement  of  the  nerve  fibres  of  the 
encephalon,  it  is  probable  that  they  run  from  one 
mass  of  grey  matter  to  another,  serving  as  commis- 
sures— but  this  is  not  positively  established.* 

*  Refer  on  this  subject  to  the  admirable  researches  "  On  the  Minute 
Structure  and  Functions  of  the  Spinal  Cord,"  by  J.  L.  C.  Shroeder  van  der 


ELEMENTS    OF    NERVOUS    TISSUE.  69 

The  ventricles  of  the  brain  and  the  aqueduct  of  Epithelium  of 

the  ventricles. 

Sylvius,  which  are  properly  to  be  regarded  as  the 
continuation,  in  the  cranium,  of  the  central  canal  of  the 
spinal  cord,  are,  like  it,  lined  by  a  layer  of  ciliated 
epithelium.  This  epithelium,  in  some  cases,  is  truly 
cjliated  only  in  the  fourth  ventricle  ;  at  least  this  is 
to  be  inferred  from  the  researches  of  Leydig  upon 
the  brain  of  a  criminal.  {Gazette  hebdomadaire,  1854,. 
"p.  687).  Beneath  the  epithelial  layer  there  are  some 
fibrillse  of  connecting  tissue  forming  an  exceedingly 
delicate  lamina,  in  which  amyloid  corpuscles  are 
found.  (Virchow.) 

The  membranes  by  which  the  cerebro-spinal  ner-  ^Sbra?dB  mai 
vous  centres  are  enveloped,  are  composed  of  con-  cord< 
nective  and  elastic  fibres,  woven  together  in  layers  of 
different  degrees  of  density.  They  have  but  few 
blood-vessels  of  their  own,  and  still  fewer  nerves ;  as 
to  lymphatics,  their  existence  has  not  even  been 
demonstrated.  The  external  surface  of  the  visceral 
layer  of  the  arachnoid  is  invested  with  pavement 
epithelium,  which  passes  from  it  upon  the  free  sur- 
face of  the  dura  mater,  where  it  alone  forms  the 
parietal  layer  of  this  serous  membrane. 

The  corpuscles  of  Pacchioni,  found  in  the  dura  corpuscles  of 

Pacchioni. 

mater  along  the  course  of  its  great  longitudinal  sinus, 
consist  of  very  dense  connecting  tissue,  enclosing 
sometimes,  in  its  meshes,  amyloid  corpuscles  and  cal- 
careous concretions.* 

Kolk,  Professor  in  the  University  of  Utrecht,  published  by  the  Eoyal 
Academy  of  Sciences  at  ^isterdam,  and  translated  and  republished  by 
the  New  Sydenham  Society,  London,  1859.— (Ed.) 

*  The  pineal  gland  contains  pale  rounded  cells_without  any  processes, 


TO  ELEMENTS^OF   NERVOUS   TISSUE. 

Development.  Nerve  fibres  are  developed,  like  the  other  tissues, 
from  embryonic  cells.  These  cells  unite  by  their 
extremities  to  form  lubes,  whilst  their  contents  are 
being  transformed  into  nervous  marrow  and  axis- 
cylinder.  We  learn  from  the  investigations  of  Kol- 
liker,  made  upon  the  tail  of  the  tadpole,  that  tl>e 
peripheral  extremities  of  nerve  fibres  take  their 
origin  independently  of  branching  or  star-shaped 
cells,  and  thus  we  have  a  clue  to  the  mode  of  forma- 
tion of  their  terminal  divisions  and  loops.  As  to  the 
development  of  nerve  cells,  it  is  effected  by  a  simple 
change  of  shape  and*  volume  of  primordial  cells. 

Nerve  fibres,  when  divided,  are  reproduced,  but 
the  exact  mode  in  which  the  process  is  accomplished 
is  not  well  ascertained.  It  is  asserted  by  some  that 
the  peripheral  extremity  of  the  injured  fibre  disap- 
pears, and  is  replaced  by  a  newly  formed  fibre ; 
others  again  suppose  that  the  medulla  alone  is  the 
seat  of  change,  and  that  the  regeneration  of  the  fibre 
is  effected  by  the  formation  of  a  new  medulla  in  the 
original  tube.  Farther  research  is  obviously  required 
for  the  elucidation  of  this  point  of  histogenesis. 

and  bnt  a  few  nerve  fibres  y^-^th  to  y^ths  of  a  line  in  diameter ;  and, 
for  the  most  part,  a  large  quantity  of  sandy  particles. 

The  pituitary  body  contains,  in  its  anterior  reddish  lobe,  no  nervous 
elements,  but  rather,  according  to  Ecker,  the  elements  of  a  vascular 
gland.  The  posterior  smaller  lobe  consists  of  a  finely  granular  substance, 
with  nuclei  and  blood-vessels,  and  possesses,  also,  fine  varicose  nerve- 
tubes,  which,  like  the  vessels,  descend  to  it  from  the  infundibulum.  K61- 
liker,  last  edition,  p.  233.— (Ed.} 


CHAPTEE   VI. 

Vessels. — Arteries. —  Veins. — Capillaries, 
and  Lymphatics. 

VESSELS  are  of  two  species :  blood-vessels  and  lyni-  classification 
phatics.  Tlie  former  are  sub-divided  into  arteries, 
capillaries,  and  veins  ;  the  latter  into  lymphatics,  pro- 
perly so  called,  and  lacteals.  The  structure  of  arte- 
ries, veins,  the  larger  lymphatics,  and  lacteals,  is 
almost  identical ;  the  same  is  true  of  the  capillaries 
and  smaller  lymphatic  vessels, 

Each  one  of  the  tissues  which  we  have  studied  thus 
far  has  some  special  or  characteristic  element;  but 
this  is  not  the  case  with  the  organs  now  under  exa- 
mination. No  anatomical  element  of  determinate 
form  belongs  exclusively  to  them  ;  but  that  which 
serves  to  distinguish  them  from  other  tissues,  is  the 
peculiar  arrangement  of  the  several  parts  of  which 
they  are- composed. 

Both  recent  and  dried  specimens  are  required  for  Preparations. 
the  examination  of  their  structure.  From  portions 
of  dried  vessels,  very  delicate  and  thin  slices  are  cut 
by  a  razor,  and  soaked  in  water  before  being  placed 
under  the  microscope.  These  sections  answer  for  the 
examination  of  the  outer  and  middle  coats,  and  for 
the  deeper  portions  of  the  internal  coat  of  large  ves- 
sels ;  but  when  we  wish  to  study  the  epithelial  layer, 


72    VESSELS. AETEEIES. VEINS. CAPILLAEIES,    ETC. 

and  vessels  of  very  small  size,  such  as  capillaries, 
recent  specimens  are  required. 

Arteries.  SECT.  I.  AETEEIES. — When  a  section,  either  trans- 
verse or  longitudinal,  including  the  whole  thickness 
of  the  wall  of  an  artery,  is  placed  under  the  micro- 
scope, we  recognise  three  distinct  strata  overlying 
each  other,  which  correspond  to  the  three  coats  of 
which  the  vessel  is  composed  (PL  XIV.  fig.  IV.). 
The  first,  which  is  the  thinnest,  and  uniformly  dark 
throughout  its  whole  thickness,  represents  the  in- 
ternal coat  (Fig.  IV.  1).  The  second  stratum,  which 
is  transparent,  and  much  thicker  than  the  first,  is  the 
middle  coat  (Fig.  IV.  2).  And,  finally,  the  third 
stratum,  at  least  as  thick  as  the  second,  and  darker 
in  its  deeper  than  in  its  more  superficial  portion,  cor- 
responds to  the  external  coat.  By  employing  a 
magnifying  power  of  300  to  400  diameters  it  is  easy 
to  make  out  the  nature,  as  well  as  the  arrangement 
of  the  elements  which  constitute  each  of  these  coats. 
The  following  is  a  summary  of  their  microscopical 
internal  coat  analysis  :  the  internal  tunic  is  limited,  on  its  free  sur- 
face, by  a  layer  of  simple  epithelium,  which,  exa- 
mined in  situ,  seems  to  consist  of  oval  nuclei,  im- 
bedded in  a  structureless  substance ;  the  walls  of  its 
cells  are  not  distinguishable  in  consequence  of  their 
extreme  paleness  (PI.  XV.  fig.  I.).  But,  by  teasing 
out  this  membrane  by  the  aid  of  needles,  some  cells 
may  be  detached,  which  are  recognizable  as  fusiform 
in  shape,  with  a  very  prominent  bulge  opposite  the 
situation  of  their  nuclei  (PI.  XV.  fig.  II.),  and  which, 
in  this  respect,  resemble  certain  cells  of  the  spleen. 
Beneath  this  epithelial  layer,  which  is  in  contact  with 


VESSELS. ARTERIES. VEIttS. CAPILLARIES,   ETC.  73 

the  blood  contained  in  xthe  vessel,  there  is  another 
lamella  known  by  the  name  of fenestrated  membrane. 
It  is  amorphous,  elastic,  traversed  by  numerous  open- 
ings which  vary  both  in  size  and  shape,  and  contains 
elastic  fibres  which  are  disposed  at  right  angles  to 
the  axis  of  the  vessel  (PL  XV.  fig.  III.  1,  2,  3,  4). 
The  deepest  layer  of  the  internal  coat  is  composed  of 
fine  elastic  fibres,  which  run  in  the  direction  of  the 
length  of  the  vessel.  This  layer  is  the  thickest  of  the 
three  laminae  which  constitute  the  internal  coat,  espe- 
cially in  the  larger  arterial  trunks  (PI.  XIV.  fig.  V. 
1 ;  PI.  XV.  fig.  III.  5 ;  fig.  IV.  1).  The  semilunar 
valves  and  the  endocardium  are  formed  by  the  in- 
ternal coat. 

The  middle  coat  is  made  up  of  elastic  fibres,  and  Middle  c^t. 
those  of  non-striated  muscle.  The  first  are  distri- 
buted uniformly  throughout  the  thickness  of  the 
layer,  but  seem  to  run  in  no  determinate  direction ; 
this  is  readily  recognised  by  comparing  transverse 
and  longitudinal  sections  under  the  microscope  (PL 
XIV.  fig.  V.  2 ;  fig.  VI.  1 ;  PI.  XV.  fig.  IV.  6).  The 
network  formed  by  these  fibres  is  closer  in  its  meshes 
in  proportion  to  the  calibre  of  the  artery  to  which  it 
belongs,  and  in  these  meshes  the  muscular  fibres  are 
contained.  To  bring  the  latter  into  view  it  is  well 
to  treat  the  specimen  with  dilute  acetic  acid.  In 
transverse  sections  it  is  difficult  to  distinguish  the 
outlines  of  these  fibres  on  account  of  their  extreme 
paleness;  but  their  nuclei,  club  shaped,  and  arranged 
perpendicularly  to  the  axis  of  the  vessel,  are  easily 
recognised  (PL  XIV.  fig.  V.  3).  In  longitudinal  sec- 
tions, the  outlines  of  the  smooth  muscular  fibres  are 

5 


Y4    VESSELS. AKTEKIES. VEINS. CAPILLARIES,  ETC 

much  better  seen;  they  form  polygons  of  variable 
regularity  of  outline,  in  which  the  central  nucleus  is 
pretty  uniformly  apparent  (PI.  XV.  fig.  IV.  4).  It 
is  to  be  remarked  that  these  muscular  fibres  are  dis- 
tributed with  perfect  regularity  throughout  the  whole 
thickness  of  the  middle  coat. 

External  coat.  The  external  coat  is  formed  by  a  close  interlace- 
ment of  connective  and  elastic  fibres,  resembling  felt. 
The  farther  from  its  outer  surface  the  greater  the 
amount  of  elastic  fibres,  and  they  generally  run 
parallel  with  the  axis  of  the  vessel  (PL  XV.  fig.  V. 
1,  2;  fig.  VI.  1,2). 

In  reviewing  the  structure  of  the  walls  of  arteries 
it  is  obvious  that  elastic  fibre  forms  the  frame-work 
of  all  their  coats ;  but  also,  that  in  each  separate  coat 
it  is  associated  with  another  distinct  and  character- 
istic element :  in  the  internal,  this  is  epithelium ;  in 
the  middle  coat,  muscular, —  and  in  the  external,  con- 
nective, fibre.  Just  in  proportion  as  we  approach 
the  smaller  terminal  arterial  branches,  the  elastic 
fibres  tend  to  disappear,  especially  in  the  middle  coat, 
which  finally  becomes  entirely  muscular  (PL  XIV. 
fig.  VII). 

In  the  last  and  smallest  branches  of  the  arterial 
tree  which  we  can  examine,  those,  for  example,  which 
measure  from  T\th  to  ~th  of  a  line  in  diameter,  we 
still  recognise  the  three  coats,  but  each  one  of  them 
is  constituted  by  only  a  single  lamella  of  tissue,  com- 
prising but  a  solitary  anatomical  element.  Thus,  the 
outer  coat  consists  of  a  very  thin  layer  of  connective 
fibres  mingled  with  some  plasmatic  cells  (PL  XV. 
fig.  VII.  1).  The  middle  coat  shows  very  short  fusi- 


VESSELS.— ARTERIES. VEINS. CAPILLARIES,  ETC.    75 

form  fibres  of  non-striated  muscle,  indicating  that,  in 
these  little  arterioles,  this  tissue  remains  permanently 
in  an  imperfectly  developed  condition  (PL  VII.  2,  3). 
As  for  the  inner  coat,  it  is  reduced  to  a  mere  layer  of 
epithelial  cells  (fig.  III.  4). 

SECT.  II.  VEINS. — The  structure  of  the  veins  fol- 
lows  the  same  general  plan  as  that  of  the  arteries. 
Like  them,  they  have  three  coats.  The  epithelial 
layer  of  the  internal  coat  is  identical  in  every  respect  internal  coat 
with  that  of  the  arteries.  In  almost  all  the  specimens 
which  I  have  examined,  a  fenestrated  membrane  has 
been  present,  showing  numerous  openings,  surrounded 
by  an  interlacement  of  large  elastic  fibres  (PI.  XVI. 
fig.  IV.  1,  2). 

Beneath  this  is  a  third  layer  of  fine  elastic  fibres, 
forming  a  somewhat  looser  web  than  the  correspond- 
ing layer  of  the  inner  coat  of  an  artery,  and  pene- 
trating, by  its  deepest  fibres,  the  surface  of  the  middle 
coat — so  that  the  dividing  line  between  these  two 
coats  is  not  so  distinct  and  clear  as  in  the  walls  of  an 
artery  (PL  XVI.  fig.  II.  2). 

The  middle  tunic  presents  an  intermixture  of  Middle  coat 
elastic  and  muscular  fibres,  but  the  latter  are  not 
uniformly  distributed  (fig.  II.  5,  6).  Their  direction 
is  generally  transverse,  but  nevertheless,  near  its 
outer  surface,  there  are  some  which  run  parallel  with 
the  axis  of  the  vessel  (fig.  II.  7,  8).  May  not  this 
unequal  distribution  of  muscular  fibre  in  the  walls  of 
veins  account  for  the  relative  weakness  of  certain 
portions  of  them,  and  thus  explain  their  tendency  to 
become  varicose  ? 

The  external  coat  is.  similar  in  every  particular  to  External  coat 


76    VESSELS. ARTERIES. VEINS. CAPILLARIES,  ETC. 

that  of  the  arteries ;  but  it  is  to  be  noticed  that  in 
certain  veins,  principally  in  those  belonging  to  the 
portal  system,  muscular  fibres  have  been  found  in  its 
deeper  portion,  longitudinal  in  their  direction.  The 
presence  of  these  muscular  fibres,  and  the  direction  of 
their  course,  explains  the  reason  why  these  veins 
diminish  in  length  under  the  influence  of  the  stimulus 
of  galvanism. 

ize.  In  veins  of  the  smallest  size  the  three  tunics  are 
still  distinguishable ;  the  innermost  is  a  simple  epi- 
thelial layer ;  sometimes,  however,  there  is  a  fenes- 
trated  layer  outside  of  it,  presenting  exceedingly 
delicate  meshes  (PI.  XVI.  fig.  V.  6).  The  remaining 
tunics  resemble  exactly  those  of  arteries  of  similar 
calibre  (fig.  V.  1,  3). 

valves.  The  valves  of  veins  are  formed  by  their  internal 
coat.  A  lamina  of  pavement-epithelium  constitutes 
their  surface  (PL  XVI.  fig.  III.  1).  More  deeply,  we 
encounter  wavy  and  parallel  fasciculi  of  connective 
fibres,  and  a  web  of  delicate  elastic  fibres  intermingled 
with  plasmatic  cells.  The  latter  are  rendered  visible 
by  the  addition  of  dilute  acetic  acid,  which  dissolves 
the  connective  fibres. 

The  vasd  vcisorum  are  arterioles  and  veinules. 
According  to  Kolliker,  they  are  to  be  found  on  ves- 
sels even  of  the  smallest  calibre  (of  the  diameter  of 
one  half  a  line  and  less) ;  they  are  distributed  mainly 
to  the  outer  coat ;  in  the  middle  coat  there  are  a  few, 
but  in  the  inner  coat  I  have  never  seen  them.  The 

Nerves,  nerves  which  supply  the  walls  of  vessels  are  few  in 
number,  and  those  which  .are  encountered  are  for  the 
most  part  destined  to  the  organs  supplied  by  the 


VESSELS. AETEEIES. VEINS. — CAPILLAEIES,  ETC. 

vessels  which  they  accompany,  rather  than  for  the 
innervation  of  the  vessels  themselves.  They  seem  to 
terminate  by  free  ends,  and  it  is  uncertain  whether 
or  not  they  reach  the  internal  coat. 

SECT.  III.  CAPILLAEIES. — The  capillary  vessels,  capillaries. 
which  are  the  media  of  communication  between  the 
arteries  and  veins,  are  exceedingly  simple  in  their 
structure.  They  are  tubules  of  structureless  sub- 
stance, studded  with  oval  nuclei.  The  larger  the  size 
of  the  capillaries,  the  thicker  are  their  walls,  and  the 
greater  the  number  of  nuclei  (PI.  XV.  fig.  VIII ;  PL 
XVI.  fig.  I.  1).  The  smallest  of  them  have  such 
exceedingly  thin  walls  that  they  are  portrayed  by 
only  a  single  line.  The  transition  from  arteries  and 
veins  to  capillaries  takes  place  insensibly,  and  by  the 
successive  disappearance  of  the  several  organized  ele- 
ments which  constitute  the  three  tunics  of  a  vessel. 

SECT.  IV.  LYMPHATIC  VESSELS. — After  what  has 
been  said  concerning  the  histology  of  arteries  and 
veins,  a  few  words  only  will  be  required  for  the 
description  of  the  structure  of  lymphatics. 

Their  internal  membrane  consists  of  a  simple  layer 
of  epithelium  supported  by  a  web  of  elastic  fibres  of 
extreme  delicacy  ;  sometimes  it  appears  to  be  reduced 
to  epithelium  alone.  .>; 

Their  middle  coat  is  composed  almost  exclusively 
of  muscular  fibres  arranged  transversely ;  elastic 
fibres  are  very  few  in  number  (PL  XVII.  fig.  II.  2, 
3).  Finally,  the  external  coat  differs  from  that,  of 
arteries  and  veins,  by  containing  a  large  amount  of 
longitudinal  muscular  fibre  in  its  deepest  portion 
(fig.  II.  5 ;  fig.  III.  5).  Their  valves  contain  also 


78    VESSELS. AKTEKIES. VEINS. CAPILLARIES,  ETC. 

some  muscular  fibres,  and  otherwise  resemble  those  of 
the  veins  (PL  XVII.  fig.  IV.  3). 

The  lymphatics,  then,  are  seen  to  present  the  same 
general  plan  of  structure  as  arteries  and  veins,  with 
this  single  feature  of  difference,  that  they  are  richer 
in  muscular  fibre.  The  lymphatic  capillaries,  like 
those  which  carry  blood,  consist  of  tubes  of  amor- 
phous substance,  with  oval  nuclei  set  in  their  walls. 
Their  characteristic  peculiarity  consists  in  the  filiform 
prolongations  which  they  give  off  at  intervals  along 
their  course,  and  at  their  terminal  extremities  (Kol- 
liker).  As  for  the  true  seat  of  origin  of  the  lympha- 
tics (that  of  the  lacteals  being  already  understood), 
it  is,  according  to  M.  Kiiss,*  immediately  beneath  the 
several  epithelial  membranes — with  the  functions 
of  which  those  of  the  lymphatics  seem  to  be  closely 
connected. 

0  ^°  *he  system  °f  lymphatic  vessels  are  attached 
the  little  gangliform  organs  known  as  lymphatic 
glands.  These  glands  possess  a  fibrous  envelope,  and 
consist,  internally,  of  a  cortical  and  a  medullary  sub- 
stance. The  cortical  substance,  which  in  section  pre- 
sents a  granular  aspect,  comprises  the  superficial  por- 
tion of  the  parenchyma  of  the  gland.  It  is  a  sort  of 
extremely  delicate  cavernous  body,  whose  trabeculse, 
consisting  of  imperfectly  developed  connecting  tissue, 
serve  to  support  the  blood-vessels  and  lymphatic 
trunks  which  enter  it.  Its  cavities  communicate  in 
every  direction  with  each  other,  with  those  of  the 

*  Professor  of  Pathological  Anatomy  in  the  Faculty  of  Medicine  of 
Strasbourg,  France. — (Ed) 


VESSELS. ARTERIES. VEINS. CAPILLARIES,  ETC.       9 

central  medullary  portion,  and  with  the  terminal 
branches  of  the  afferent  lymphatics  ;  they  contain  an 
alkaline  liquid,  and  organized  corpuscles,  amongst 
which  we  can  distinguish  little  cells,  averaging  ai^th 
of  a  line  in  diameter,  and  spherical  granular  nuclei  of 
from  4^oth  to  ^oth  of  a  line.  These  elements  are 
identical  with  those  which  exist  in  lymph  and  chyle. 

The  medullary  substance,  striated  in  appearance,  is 
enveloped  on  all  sides  of  the  cortical  substance,  except 
at  those  points  where  the  afferent  vessels  enter  the 
gland.  It  is  made  up,  mainly,  of  the  terminal  radi- 
cles of  the  afferent  vessels,  which,  taking  their  origin 
in  the  deeper  cavities  of  the  cortical  substance,  anas- 
tomose with  each  other  and  form  a  network,  whose 
branches,  becoming  gradually  larger  in  size,  and 
fewer  in  number,  finally  terminate  in  one  or  two 
efferent  lymphatic  vessels,  which  make  their  exit  at 
the  hilus  of  the  gland. 

The  arteries,  most  of  which  terminate  in  the  cor- 
tical substance,  either  arrive  there  directly,  or  after 
traversing  the  medullary  portion  of  the  organ,  to 
which  they  give  off  a  few  branches.  In  the  trabeculse 
of  the  cortical  substance  these  vessels  form  an  intri- 
cate capillary  plexus,  which  is  directly  in  contact 
with  the  cells  of  the  gland. 

The  veins,  fewer  in  number  and  greater  in  volume 
than  the  arteries,  accompany  them  in  their  course. 
The  nerves  are  not  numerous ;  they  enter  the  gland 
with  its  vessels,  and  their  mode  of  termination  is 
unknown. 

The  structure  of  a  lymphatic  gland  may  be  summed 
(up  as  follows:  the  essential  or  secreting  portion  of 


80    VESSELS. AKTEKIES. VEINS. — CAPILLARIES,  ETC. 

the  gland  is  represented  by  a  large  cavity  (cortical 
substance)  filled  with  globules,  which  are  imbedded 
in  a  vascular  network,  from  which  they  extract  mate- 
rial for  elaboration.  On  one  side,  this  cavity  is  in 
communication  with  the  afferent  lymphatic  vessels, 
and  on  the  other,  with  the  efferent  vessels,  into  which 
latter  it  pours  the  organized  products  which  after- 
wards become  white,  and  perhaps,  also,  red  globules 
of  the  blood. 

?ee8Iei8pmefit  of  Arteries,  veins,  and  lymphatic  vessels  are  alike 
developed  from  embryonic  cells.  They  are  at  first 
recognisable  in  the  shape  of  rows,  or  columns,  of  cells. 
Of  the  cells  which  correspond  to  the  axis  of  the 
column,  one  portion  liquifies,  and  the  remainder 
becomes  transformed  into  blood  globules.  Those 
which  lie  on  either  side  of  the  axis  undergo  various 
changes,  and  finally  form  the  three  coats  which  con- 
stitute the  walls  of  the  vessel. 

The  development  of  capillary  vessels  is  accom- 
plished in  the  following  manner :  cells  of  oval  shape 
become  united  to  each  other  end  to  end,  and  then  the 
partitions  which  separate  them  are  absorbed  and  dis- 
appear ;  so  that  each  series  of  cells  is  thus  trans- 
formed into  a  minute  canal,  in  the  structureless  walls 
of  which  nuclei  are  to  be  recognised,  at  regular  inter- 
vals, as  in  the  fully  formed  capillaries  of  the  adult. 
Anastomoses  are  effected  by  means  of  minute  prolon- 
gations, like  canaliculi,  which  take  their  origin  from 
the  walls  of  the  vessel,  and,  pushing  out  in  different 
directions,  unite  finally  with  each  other. 

Kolliker  has  also  demonstrated  that  branching 
plasmatic  cells  not  unfrequently  form  a  connexion,  by 


VESSELS. ARTERIES. VEINS. — CAPILLARIES,  ETC.    81 

their  prolongations,  with  the  walls  of  capillaries 
already  in  existence,  and  thus  contribute  to  the  for- 
mation of  the  capillary  plexus,  or  network.  Their 
prolongations,  increasing  in  diameter,  ultimately 
become  true  capillary  vessels,  and  the  body  of  the 
cell  itself  corresponds  to  the  point  of  confluence  of 
several  vascular  canals.  The  same  author  asserts  that 
many  large  vessels  are  formed  out  of  capillaries,  by 
the  transformation  of  the  cells  which  surround  them 
into  their  several  tunics. 

BLOOD  AISTD  LYMPH. — In  a  histological  point  of  view  j^°pdhand 
the  composition  of  blood  and  lymph  is  exceedingly 
simple.  The  organized  elements  of  the  blood  are  of 
two  species,  red  and  white  globules.  The  red  glo- 
bules are  bi-concave  discs  measuring,  on  an  average, 
aajth  to  3i<rth  of  aline  in  breadth,  and  Worth  to  TTO  o-th 
of  a  line  in  thickness.  Their  external  envelope  is  so 
exceedingly  delicate  that  it  seems  to  be  continuous 
with  their  contents.  They  consist  internally  of  an 
amorphous  substance  of  some  density,  very  elastic, 
and  colored  yellowish  red  by  hsematine.  When 
exposed  to  the  air  these  globules  become  rapidly 
altered  in  form,  and  as  a  common  rule,  show  wrinkles, 
or  indentations,  upon  their  surfaces  (PL  I.  fig.  I.  3). 
The  red  globules,  according  to  Schmidt,  constitute 
'about  one  half  of  the  whole  mass  of  the  blood. 

The  white  globules  of  the  blood  differ  from  the  white  giobuiea. 
preceding,  both  in  size  and  shape.  They  are  sphe- 
rical corpuscles,  with  rough  or  tuberculated  surfaces, 
and  average  in  diameter  from  2¥<rth  to  rioth  of  a  line 
(PI.  I.  fig.  I.  4).  Their  contents,  granular  and  trans- 
parent, include,  sometimes,  a  nucleus  so  large  as  to 


82    VESSELS. AKTEKIES. VEINS. — CAPILLARIES,  ETC. 

almost  fill  the  globule,  but  most  frequently  it  is 
represented  by  several  vesicles  of  brilliant  appear- 
ance, which  are  rendered  still  more  apparent  by  the 
addition  of  acetic  acid.  Up  to  the  present  time  dis- 
tinctive features  between  these  globules,  and  those  oi 
pus,  have  been  sought  for  in  vain.  The  relative  pro- 
portion, in  the  blood,  of  white  to  red  globules,  accord- 
ing to  Moleschott,*  is  1  to  357.  In  some  cases  oi 
leucocythemia,  it  is  increased  to  one-third,  or  even  to 
two-fifths  of  the  globular  element  of  the  blood  (Vir- 
chow). 

The  liquid  portion,  or  plasma  of  the  blood,  coagu- 
lates after  escaping  from  the  blood-vessels.  One  por- 
tion remains  liquid,  and  the  other  assumes  the  form 
of  a  consistent  and  elastic  mass — the  clot.  In  the 
serum,  or  liquid  portion,  a  few  red  and  white  globules 
are  to  be  seen  floating  in  the  colorless  fluid.  The 
clot,  which  entangles,  and  consequently  includes,  the 
great  mass  of  the  globular  elements  of  the  blood,  is 
composed,  in  addition  to  them,  of  a  substance  of  a 
very  finely  granular  or  fibrillated  appearance,  but  not 
organized  (fibrine). 

Lymph  giobuies.  The  solid  elements  of  lymph  are  globules,  whicl 
resemble  exactly  the  globules  contained  in  the  cor- 
tical portion  of  the  lymphatic  glands,  and  the  whitt 
globules  of  the  blood.  These  corpuscles,  which  ave 
rage  in  diameter  from  2  srth  to  T^th  of  a  line,  arc 
found  in  considerable  quantity  in  the  vessels  whicl 
emerge  from  the  lymphatic  glands,  whilst  in  the  affe- 
rent lymphatics,  or  those  which  enter  the  gland  and 

*  Professor  of  Physiology  in  the  University  of  Zurich. — (Ed.} 


VESSELS. ARTERIES. VEINS. CAPILLARIES,  ETC.-   83 

form  its  capillary  network,  there  are  very  few.  There 
is  found  also,  in  the  lacteals,  a  variable  quantity  of 
spherical  granules  of  an  oily  nature,  which  are  derived 
from  the  food,  and  which  are  very  early  to  be  seen  in 
the  true  lymphatics. 

Lymph,  also,  coagulates  when  it  escapes  from  its 
containing  vessel,  forming  a  clot,  identical  in  its  com- 
position to  that  of  the  blood — including,  of  course, 
no  red  globules.  Kolliker  asserts  that  lymph  never 
contains  red  globules,  and  that  those  occasionally 
found  in  it  got  there  in  consequence  of  the  rupture  of 
a  blood-vessel. 

The  formation  of  the  red  blood  corpuscles  in  the  F1°™fet£mofred 
embryo  is  effected,  as  we  have  already  stated,  by 
transformation  of  the  primordial  or  embryonic  cells 
which  occupy  the  centre  of  the  blood-vessels  whilst 
in  process  of  development.  These  cells  are  not  at  first 
distinguishable  from  the  embryonic  cells  by  which 
they  are  surrounded,  but  they  soon  become  infiltrated 
with  haematine,  flatten  out  into  discs,  and  their  nuclei 
tend  to  disappear.  They  multiply  by  the  process  of 
cleavage.  In  the  adult  the  increase  in  number  of  red 
corpuscles  seems  to  take  place  at  the  expense  of  the 
lymph  globules,  which  become  disc-like  in  shape,  and 
charged  with  haematine,  whilst  at  the  same  time 
their  nuclei  are  absorbed.  Kolliker,  relying  upon 
what  he  has  observed  in  the  lower  animals,  asserts 
that  this  is  the  mode  of  development  of  the  red  cor- 
puscles of  the  blood  in  man. 


• 


CHAPTEK    VII. 
Glands. 

Definition.  GLANDS  are  organs  which  present  a  great  variety 
in  their  size  and  shape ;  they  consist  essentially  of 
enclosed  cavities,  lined  or  filled  with  cells,  and  open- 
ing upon  the  surface  of  the  skin,  or  of  a  mucous 
membrane,  either  directly,  or  by  means  of  special 
canals  known  as  their  excretory  ducts. 

Certain  organs  composed  of  one  or  more  cavities, 
closed  on  all  sides,  and  filled  by  cells  or  globules,  are 
called  blood-glands,  and  duct-less  follicles. 

The  parenchyma  of  glands  (the  essential  or  secret- 
ing portion  of  the  organ)  is  made  up  either  of  tubes, 
or  of  partially  closed  vesicles,  grouped  together  in 
parcels,  like  clusters  of  fruit,  and  opening  into  a 
common  canal  or  outlet.  Hence  we  speak  of  two 
sorts  of  glands :  those  composed  of  clusters  of  vesi- 
cles (racemose),  and  tubular  glands. 

General  struc-  Generally  glands  are  invested  externally  by  an 
envelope  of  connecting  tissue,  varying  in  density. 
From  the  deep  surface  of  this  external  envelope, 
processes  or  trabeculse  are  given  off,  which,  traversing 
the  interior  of  the  organ  in  different  directions,  divide 
up  the  glandular  parenchyma  into  segments  (lobes, 
lobules);  they  also  support  the  vessels  and  nerves  of 
the  organ.  The  vesicles  and  secreting  tubes  are 
formed  by  a  membrane  of  their  own  (basement  mem- 


ture. 


GLANDS.  85 

brane),  which  is  usually  very  delicate  and  structure- 
less ;  sometimes  it  is  more  dense,  being  strengthened 
externally  by  a  layer  of  fibrillated  tissue  (as  in  the 
testicles,  lungs,  etc.).  Its  internal  surface  is  covered 
by  a  simple  layer  of  epithelial  cells,  generally  many- 
sided  ;  or,  these  are  arranged  in  strata,  so  as  to  fill 
completely  the  cavities  of  the  secreting  vesicles,  or 
tubules.  Upon  the  external  surface  of  their  basement 
membrane  blood-vessels  ramify,  so  as  to  form  a  capil- 
lary web,  or  network,  with  meshes  of  varying  size 
in  different  glands. 

Nerves  accompany  the  blood-vessels,  but  aTe  rela- 
tively  less  numerous ;  their  mode  of  termination  is 
not  yet  fairly  known,  but  it  is  probably  by  means  of 
free  extremities. 

The  excretory  canals,  or  ducts,  of  glands,  have  an  Ducts, 
external  coat  which  is  usually  formed  by  the  inter- 
lacement of  connective  and  elastic  fibres,  together 
with  fibres  of  unstriped  muscle ;  internally  they  are 
lined  by  an  epithelial  layer,  the  cells  of  which  diifer 
from  those  of  the  parenchyma  of  the  gland.  The 
ducts  of  some  glands  contain  minute  clusters  of  vesi- 
cles in  the  thickness  of  their  walls  (liver,  pancreas, 
lung). 

SECT.  I.  GLANDS  CONSISTING  OF  CLUSTERS  OF  VESI-  Glands  formed  bj 

clust*8  of  vesi- 

CLES. — The  glands  of  this  variety  scarcely  differ  from  cles- 
each  other  in  structure,  except  in  the  minute  details 
which  belong  to  the  disposition  and  arrangement  of 
their  epithelial  element.  Therefore,  in  order  to 
escape  the  useless  repetitions  which  a  separate  de- 
scription of  each  gland  would  of  necessity  involve, 
we  shall  study  the  structure  of  certain  individual 


86  GLANDS. 

glands,  which  will  then  serve  as  types,  around  which 
those  of  similar  structure  will  naturally  group  them- 
selves. And  let  us  commence  by  examining  those  of 
simplest  structure,  e.  g.  the  salivary  glands, 
salivary  glands,  /Salivary  Glands. — On  placing  a  very  thin  section 
of  the  sub-lingual  gland  under  the  microscope,  we  see 
that  its  terminal  cul-de-sacs,  or  ccecal  pouches,  are 
incomplete  vesicles,  the  walls  of  which  are  formed  by 
two  layers.  The  external  layer  is  basement  mem- 
brane, structureless  and  exceedingly  thin,  being  only 
TeVoth  of  a  line  in  thickness.  Its  inner  lining  con- 
sists of  a  layer  of  many-sided  cells,  with  extremely 
pale  outlines,  and  averaging  in  diameter  aiirth  of  a 
line.  Their  nuclei  are  much  more  distinct,  and  so 
large  as  to  almost  fill  the  cells  (PL  XVIII.  fig.  I.  1). 
Three  or  four  of  these  vesicles,  connected  -together 
closely  in  a  group,  have  an  outlet  in  common,  and 
constitute  thus  a  microscopic  lobule.  Several  of  these 
minute  excretory  canals,  each  with  its  corresponding 
lobule,  meet  together  in  a  canal  of  somewhat  larger 
size,  and  by  their  union  form  a  lobule  large  enough 
to  be  seen  by  the  naked  eye  (PL  XVII.  fig.  V). 
Finally,  the  aggregation  of  a  number  of  lobules,  with 
a  canal  of  proportionate  size,  results  in  the  formation 
of  lobes,  and  these,  in  their  turn,  uniting  in  a  common 
excretory  duct,  make  up  the  gland.  The  excretory 
duct  is  composed  externally  of  a  coat  of  connecting 
tissue,  and  internally  of  a  layer  of  cylindrical  epithe- 
lium. The  gland  is  enveloped  .by  a  membranous 
expansion  of  connecting  tissue,  from  the  internal  sur- 
face of  which  laminated  processes  are  sent  into  the 
substance  of  the  organ,  where  they  invest  the  exte- 


GLANDS.  87 

rior  of  its  lobules  and  lobes,  and  convey  to  them,  at 
the  same  time,  their  blood-vessels  and  nerves. 

The  vessels  terminate  in  a  rich  web  of  capillaries  Jeersv6^8  and 
which  is  spread  out  upon  the  external  surface  of  the 
vesicles.     The  nerves  ramify  with  the  larger  vascular 
trunks  of  the  gland,  but  do  not  appear  to  reach  their  • 
terminal  secreting  pouches.     We  know  little  or  no- 
thing of  the  sources  of  distribution  of  the  lymphatics. 

To  this  first  type  are  assimilated  the  salivary  glands 
and  mucous  follicles  which  belong  to  the  cavities  of 
the  mouth,  pharynx,  and  oesophagus,  the  glands  of 
Brunner  in  the  duodenum,  the  lacrymal  glands,  the 
mucous  follicles  of  the  conjunctiva,  vagina,  and  vulva, 
the  glands  of  Bartholinus  and  Cowper,  and,  finally, 
those  clusters  of  vesicles  which  have  been  mentioned 
as  imbedded  in  the  walls  of  the  ducts  of  the  liver, 
pancreas,  and  lung. 

The  Lungs. — The  bronchial  tubes,  as  is  well  known,  Lung* 
form  a  tree,  whose  principal  branches  are  given  off 
from  their  trunks  at  an  acute  angle,  whilst  their  ter- 
minal ramifications  are  detached  from  the  penultimate 
branches  at  right  angles.  On  examining  the  walls  of 
these  little  terminal  ramifications  upon  their  internal 
surface,  they  are  seen  to  be  full  of  minute  openings, 
which  lead  into  cavities  (primary  lobules),  measuring 
about  aVth  of  an  inch  in  mean  diameter,  and  which 
present  a  somewhat  complicated  structure.  Each  of  Primary  iobuie». 
these  primary  lobules  resembles  one  of  the  lungs  of 
the  frog ;  on  its  inner  surface  we  recognise  large 
depressions,  or  partially  formed  vesicles  (PL  XIX. 
fig.  T.  1),  each  divided  into  three  or  four  secondary 
vesicles  (fig.  I.  2),  which  open  by  large  orifices  into 


88  GLANDS. 

the  common  cavity.  But  this  latter,  instead  of  being 
a  large  empty  space  in  the  centre  of  the  lobule,  such 
as  we  see  in  the  frog's  lung,  forms  a  sort  of  corpus 
cavernosum,  or  cavernous  sinus,  by  the  anastomosis  of 
numerous  trabeculce  which  traverse  its  interior,  and 
which  are  given  off  from  the  walls  of  the  vesicles. 

•  I  am  of  opinion,  however,  that  all  of  the  lobules 
of  the  lung  are  not  constructed  exactly  after  this 
model;  some  of  them  seem  to  be  mere  diverticula 
from  the  bronchial  walls,  presenting  vesicular  depres- 
sions upon  their  internal  surfaces,  but  without  the 
trabeculce,  resembling,  in  short,  more  perfectly,  the 
lung  of  the  frog.     We  can  often  detect  lateral  open- 
ings near  the  summit  of  a  lobule,  by  means  of  which 
it  communicates  with  neighboring  lobules ;  but  the 
number  of  these  orifices  is  limited.* 

*  In  a  monograph  published  within  the  present  year  (The  Anatomy  of 
the  Human  Lung,  an  Essay  for  which  was  awarded  the  Fothergillian 
gold  medal  of  the  Medical  Society  of  London,  by  A.  T.  HOUGHTON  WA- 
TEES,  Lecturer  on  Anatomy,  &c.,  &c.,  Liverpool.    Lond.,  1860),  contain- 
ing the  results  of  a  considerable  amount  of  original  research,  the  true 
respiratory  structure  of  the  lung  is  somewhat  differently  described.     The 
trabeculce,  forming  by  their  anastomoses  a  species  of  corpus  cavernosum 
in  the  common  cavity  of  the  primary  lobules,  are  not  recognised.     The 
following  quotations,  slightly  condensed  from  the  author's  own  language, 
give  the  result  of  his  investigations.     In  regard  to  preparations,  he  says 
(p.  168) :  u  The  plan  I  have  adopted,  and  which  I  believe  affords  the  best 
means  for  investigating  the  lung  tissue,  consists  in  the  injection  of  a 
colored  solution  of  gelatine  into   the   blood-vessels,  inflation  of  the  air- 
tubes,  and  gradual  desiccation.      In  my  first  attempt  I  inflated  the  air- 
tubes  before  injection  of  the  blood-vessels,  but  I  afterwards  injected 
before  inflation.     The  colors  I  have  used  have  been  red,  yellow,  and 
blue.     The  red,  a  finely  powdered  vermilion ;    the  yellow,  a  chromate  of 
lead,  formed,  at  the  time,  by  the  decomposition  of  acetate  of  lead  by 
bichromate  of  potash ;  the  blue,  a  Prussian  blue,  formed  by  the  decom- 
position of  ferro-cyanide  of  potassium  and  sesquichloride  of  iron.     When 


GLANDS.  89 

J 

The  primary  lobules,  thus  described,  grouped 
together  without  any  intermediate  substance,  consti- 
tute secondary  lobules.  These  latter  have  the  shape 
of  pyramids,  whose  bases  are  directed  towards  the 

a  piece  of  lung  is  well  injected,  the  walls  of  the  air-sacs  become  almost 
entirely  opaque  ;•  their  outline  may  be  distinctly  seen  when  they  are 
divided ;  and,  the  vessels  in  their  walls  being  filled  with  the  dried  gelatine 
and  coloring  matter,  dissections  under  the  microscope  can  be  carried  on 
with  great  facility,  without  which  I  believe  it  is  impossible  to  form  a 
definite  notion  of  the  anatomy  of  these  parts."  With  respect  to  injection 
of  the  air-tubes,  he  remarks  that,  "  when  gelatine  is  used  as  a  vehicle  for 
injecting  the  blood-vessels  with  some  opaque  matter,  it  usually  happens 
that  the  coloring  matter  is  left  in  the  vessels,  and  a  portion  of  the  trans- 
parent gelatine  exudes  into  the  air-tubes ;  and  this  has  appeared  to  me 
as  good  a  way  as  any,  of  effecting  an  injection  of  this  kind.  Where  such 
a  preparation  is  dried,  and  then  soaked  in  spirit  and  water,  it  swells,  and 
assumes  much  the  shape  it  has  in  its  normal  condition,  and  much  infor- 
mation may  be  derived  from  an  examination  of  it.  When  a  piece  of 
lung,  in  which  the  blood-vessels  are  injected,  has  injected  into  its  air- 
tubes  a  mixture  of  turpentine  and  wax,  and  is  left  to  dry,  and  then  a 
slice  of  it  moistened  with  Canada  balsam,  as  suggested  in  Adriani's  thesis 
(Arius  Adriani,  Dissertatio  anatomica  inauguralis  de  subtiliori  Pulmo- 
num  structurd,  1847,  p.  41),  the  substance  filling  the  air-tubes  becomes 
transparent,  and  the  outline  of  the  air-sacs  and  ultimate  bronchial  tubes 
is  well  seen,  and  a  very  correct  notion  of  their  shape  can  be  formed." 
.  .  .  .  "  If  we  follow  out  a  bronchial  tube  on  a  lung  thus  injected, 
inflated,  and  dried,  and  trace  it  to  its  termination  in  the  ultimate  air- 
tubes  or  cavities,  by  carefully  removing  the  portions  of  lung  which  are 
upon  it,  and  then  the  other  half  of  its  wall,  so  as  to  lay  bare  its  interior, 
we  adopt,  I  believe,  the  best  plan  of  ascertaining  how  the  tube  itself  ter- 
minates, in  what  manner  the  air  cavities  proceed  from  it,  and  what  rela- 
tion they  bear  to  it.  For  this  purpose,  we  should  expose  a  bronchial 
tube,  from  its  entrance  into  a  lobule,  to  its  termination.  We  find  that 
the  bronchial  tube,  having  entered  its  lobule,  divides  and  gives  off 
branches,  and  at  last  terminates  in  a  dilatation,  which  has  opening  into 
it  a  number  of  orifices.  These  orifices  lead  to  a  number  of  canals,  which 
have  been  variously  designated :  '  intra-lobular  bronchial  ramifications' 
(Addison,  PhilosopTiical  Transactions,  1842);  '  lobular  passages'  (Todd 
and  Bowman,  v.  ii.  p.  390);  'intercellular  passages'  (Rainey  on  the 

6 


90  GLANDS. 

surface  of  the  lung,  whilst  their  summits  are  conti- 
nuous with  the  bronchial  passages.  They  are  sepa- 
rated by  a  delicate  interstitial  lamina  of  connecting 
tissue.  Their  diameter  often  reaches  two-thirds  of  an 

minute  structure  of  the  lungs,  Med.   Chir.   Trans.,  vol.  xxviii.  1845) ; 
'  infundibul  urns'  (Kossignol,  Recherches  sur  lastructureintim.edu  Poumon 
de  VJiomme,  etdes  principaux  mammiferes,  Brussels,  1846)  ;  '  Halpigliian 
vesicles'  (Moleschott,  de  MalpigManis  Pulmonum  vesiculis,  Heidelberg, 
1845) ;  and  *  terminal  cavities'  (Mandl,  Anat.  Mivroscop.  t.  ii.  cb.  vi.).7  " 
To  all  of  these  terms  the  author  objects,  as  not  expressing  clearly  the 
nature  of  the  structure  they  are  intended  to  designate ;  and  after  dis- 
cussing and  rejecting  them  seriatim,  proposes,  although  unwillingly,  a 
new  term  which,  he  believes,  expresses  in  a  "shorter  and  more  exact 
manner  than  any  previously  used,  the  particular  character  and  arrange- 
ment of  the  portion  of  the  lungs  under  consideration :"  this  term  is 
" air-sacs"     " The  air-sacs  are  those  tubes  In  which  the  bronchial  rami- 
fications end  ;  they  are  situated  at  the  surface,  and  throughout  all  parts 
of  the  lung;  they  are  supported  externally  by  the  pleura,  and  within  the 
lung  they  in  part  rest,  by  their  extremities  or  their  sides,  against  the 
bronchial  tubes  and  branches  of  the  blood-vessels,  and  they  are  visible 
through  the  transparent  coats  of  the  smaller  bronchial  tubes,  as  through 
the  pleura.     The  air-sacs  consist  of  somewhat  elongated  cavities  which 
communicate  with  the  bronchial  ramification  by  a  circular  opening,  usu- 
ally smaller  than  the  cavities  into  which  it  leads,  and  which  has  some- 
times the  appearance  of  a  circular  hole  in  a  diaphragm,  or  as  if  it  had 
been  punched  out  of  a  membrane  which  had  originally  closed  the 
entrance  to  the  sac;  when  this  is  the  case  the  sac  dilates  suddenly 
beyond  the  orifice.     The  sacs  are  arranged  in  groups  (usually  from  six  to 
ten  composing  a  group,  p.  144) ;  they  are  placed  side  by  side,  and  sepa- 
rated from  each  other  by  their  membranous  walls ;  their  shape,  when 
properly  inflated,  or  when  distended  by  some  material  which  has  set  in 
the  sacs,  such  as  gelatine,  or  a  mixture  of  wax  and  turpentine,  is  polygonal ; 
they  approach  very  nearly  to  the  circular  form,  but  in  consequence  of 
their  mutual  pressure,  their  parietes  become  somewhat  flattened.     They 
increase  somewhat  in  size  as  they  pass  from  the  bronchial  tubes  to  their 
fundus,  the  latter  being  usually  the  broadest  part  of  the  sac;  but  they 
are  often  found  to  have  an  almost  uniform  diameter  throughout.     All  the 
sacs  pass  from  the  extremity  of  the  bronchial  tube  towards  the  circum- 
ference of  the  lobule  in  which  they  are  placed ;  they  consequently  radiate 


GLANDS.  91 

inch,  or  more.  In  the  adult,  as  a  rule,  the  outline  of 
the  bases  of  these  lobules  is  marked  on  the  surface  of 
the  lung  by  a  variable  amount  of  black  pigmentary 
deposit, 

from  the  tip  of  each  terminal  bronchial  twig.  The  sacs  connected  with 
one  "bronchial  termination  do  not  communicate  with  those  of  another  ; 
each  set  of  air-sacs  is  therefore  a  little  lobule,  or  lobulette,  which,  in  fact, 
represents  the  entire  arrangement  of  the  lung,  and  is  a  lung  in  miniature." 
(The  resemblance  of  a  lobulette  to  the  entire  lung  of  a  frog,  is  elsewhere 
strongly  emphasized.)  "  As  the  air-nacs  pass  towards  the  boundary  of 
the  lobulette,  they  often  bifurcate,  and  here  and  there  circular  orifices 
exist,  which  lead  to  smaller  sacs,  sometimes  only  to  a  small  group  of  air- 
cells  or  alveoli,  so  small  as  scarcely  to  be  considered  a  sac."  The  author 
adopts  the  term  alveolus  from  Rossignol  as  preferable  to  air-cell,  or  air- 
vesicle,  both  of  which  he  considers  objectionable.  "  A  pulmonary  alve- 
olus is  that  portion  of  an  air-sac  which  exists  in  its  wall,  and  is  circum- 
scribed by  a  slightly  raised  margin,  consisting  of  thin  membrane,  and 
constituting  a  cup-like  depression.  In  shape  it  is  more  or  less  polygonal. 
The  alveoli  are  found  throughout  the  circumference  of  the  sacs,  and  at 
their  fundus,  varying  in  number  in  each  sac  from  eight  to  twenty.'"1 
u  If  we  trace  the  sacs  from  their  fundus  we  may  say  that,  passing  from 
the  periphery  of  the  lobulette,  and  diminishing  somewhat  in  size,  they  all 
terminate  in  the  dilated  extremity  of  the  bronchial  tube,"  by  the  common 
orifice  already  described.  "  The  sac?,  as  they  pass  in  this  manner,  often 
join,  two  and  three  together,  and  others  terminate  in  a  single  mouth." 
.  .  .  .  "  The  tube  which  results  from  the  union  of  two  sacs  has  a 
smaller  capacity  than  that  of  the  two  sacs  taken  together,  but  a  larger 
capacity  than  either  of  them  individually."  ....  "The  shape  of 
these  groups  of  air-sacs,  or  lobulettes,  is  more  or  less  pyriform,  the  apex 
being  situated  at  the  termination  of  the  bronchial  tube ;  the  base, 
somewhat  flattened,  especially  at  the  superficies  of  the  lung,  at  the  distal 
extremity  of  the  sacs.  A  most  excellent  way  of  examining  the  air-sacs^ 
and  one  which  demonstrates  most  satisfactorily  the  manner  in  which  those 
at  the  surface  of  the  lungs  are  arranged  with  reference  to  the  bronchial 
tubes,  is  the  following :  a  thin  slice  should  be  cut  off  the  surface  of  a 
portion  of  lung  which  has  beerr  injected,  inflated,  and  dried,  and  the 
portion  itself  (not  the  slice)  should  then  be  placed  under  the  dissecting 
microscope.  The  cut  orifices  of  the  air-sacs  will  be  observed.  Very 
fine  bristles  should  then  be  inserted  into  these  tubes,  the  largest  one  being 
first  chosen.  It  will  be  found  that  several  of  the  bristles,  passing  into 


92  GLANDS. 

structure  of^the       The  constituent  parts  of  a  pulmonary  vesicle,  pass- 
ing from  without  inwards,  are,  1st,  basement  mem- 
brane;   2d,  its  epithelial   investment.     The   first   is 
.  formed  by  an  extremely  delicate  web  of  elastic  fibres ; 

different  openings,  converge  to  a  point  a  short  distance  from  the  surface 
of  the  lung.  It  will  be  known  that  they  pass  to  a  common  point,  as,  by 
moving  one  of  the  bristles  gently,  it  will  act  upon  the  others.  Having 
placed  bristles  in  all  the  air-sacs  which  converge  to  this  spot,  the  bristles 
should  be  left  in  their  position,  and  the  bronchial  tube  should  be  laid 
bare  on  its  proximal  side,  down  to  its  termination,  i.  e.  the  lung  sub- 
stance covering  it  should  be  removed,  care  being  taken  to  stop  just 
before  reaching  the  spot  where  it  communicates  with  the  air-sacs.  The 
number  of  bristles  communicating  with  the  spot  thus  exposed,  will  show 
the  number  of  air-sacs  belonging  to  one  group.  The  termination  of  the 
bronchial  tube  will  be  seen  to  be  somewhat  expanded,  and  the  air-sacs 
will  be  found,  many  of  them,  to  communicate  with  it  by  a  circular  ori- 
fice, which  is  smaller  than  the  sac  itself."  .  .  .  .  "  When  the  bron- 
chial tube  has  been  exposed  in  the  way  I  have  mentioned,  and  the  mode 
of  communication  with  the  air-sacs  observed,  a  section  may  be  made 
longitudinally  through  one  or  more  of  the  latter ;  it  will  be  then  seen 
that  the  sacs  lie  side  by  side,  and  that  they  occasionally  give  off  smaller 
sacs ;  the  manner  also  in  which  they  divide,  and  the  mode  in  which 
they  terminate,  will  be  observed.  It  will  also  be  seen,  that  as  each 
bronchial  tube  approaches  its  termination,  it  has  here  and  there  through- 
out its  circumference,  small  circular  orifices,  which  are  the  commencement 
of  small  canals,  leading  to  groups  of  air-sacs  or  lobulettes ;  and  it  will 
further  be  seen  that  the  tube  itself,  at  its  termination,  has  a  number  of 
alveoli  in  its  walls.  .  .•  . 

"  Another  very  excellent  way  of  examining  the  terminal  bronchial 
tubes,  and  the  commencement  of  the  air-sacs,  is  to  soak  a  piece  of  lung 
that  has  been  injected,  inflated,  and  dried,  in  spirits  for  some  time,  and 
when  the  piece  is  well  saturated,  to  dissect  it  under  the  microscope.  By 
imbibition  of  the  spirit  the  mass  of  lung  swells,  and  the  air  tubes  and  sacs 
remaining  distended,  the  parts  assume  nearly  the  size  and  shape  they  have 
in  life.  When  such  a  piece  is  examine^,  very  frequently  on  opening  the 
bronchial  tubes  and  following  them  to  their  end,  their  alveoli  may  be 
plainly  seen,  as  well  as  the  orifices  leading  to  the  air-sacs,  and  the  band 
of  elastic  fibres  which  surrounds  the  opening  into  each  sac  becomes 
apparent."— pp.  182-14T.— (Ed.} 


GLAKDS.  93 

these  accumulate  in  the  intervesicular  partitions,  and 
form  likewise  the  central  portions  of  the  trabeculse 
PL  XIX.  fig.  II.  1).  The  nature  of  this  membrane 
explains  the  great  elasticity  of  the  lungs. 

The  epithelial  lining  of  the  pulmonary  vesicles  is  Epithelium. 
composed  of  many-sided  cells  with  very  pale  outlines, 
measuring,  in  mean  diameter,  ai^th  of  a  line,  and 
having  no  cilia ;  their  nuclei  are  very  large  (2 ijth  of 
a  line)  and  full  of  dark  granules  (PL  XIX.  fig.  II.  2  ; 
fig.  III.).  This  epithelial  layer  is  found  also  upon  the 
trabeculse.  I  have  reason  to  believe  that  fatty  dege- 
neration of  these  epithelial  cells  always  constitutes 
the  initial  lesion  of  pulmonary  tuberculosis.* 

In  tracing  the  epithelium   from   the  vesicles  and  ^'nayer epi" 
lobules  into  the  bronchial  tubes,  the  single  layer  of 
cells  becomes  double,  and  the  number  of  strata  con- 
tinues to  increase  as  the  air-tubes  enlarge  in  calibre ; 

*  The  existence  of  an  epithelial  lining  toBthe  air-cells  of  the  lungs  is  one 
of  the  most  recently  established  facts  of  histological  science.  It  is  denied 
by  recent  and  high  authorities,  viz.  Kainey  (Med.  CMr.  Trans,  vol.  xxxii. 
1849,  p.  51 ;  and  Brit,  and  For.  Med.  CMr.  Rev.  No.  xxxii.  p.  491),  and 
Todd  and  Bowman  (Phys.  Anat.,  Lond.  1856,  vol.  ii.  p.  391) ;  although 
the  latter  admits  the  fact  in  his  article  on  "  Mucous  Membranes"  in  the 
Cyclopaedia  of  Anatomy.  It  is  asserted  by  Carpenter  (Human  Physio- 
logy, p.  513,  4th  Ed.  Lond.),  by  Quain  and  Sharpey,  Kolliker,  Rossignol, 
Adriani,  Schroeder  van  du  Kolk,  Schultz  (Disqumt.  de  structured  et  tex- 
turd  canalium  ariferorum,  1850,  p.  10) ;  Williams  (art.  Lungs  in  Cyclo- 
pedia of  Anatomy,  1855)  ;  Dr.  Radclyffe  Hall  (Brit,  and  For.  Med.  CMr. 
Rev.  No.  xxx.  p.  481) ;  Mandl  (Anat  Micros,  vol.  ii.  p.  327) ;  Milne 
Edwards  (Lemons  sur  la  Physiologie,  &c.,  t.  ii.,  p.  326)  ;  Peaslee  (Human 
Histology,  &c.,  &c.,  Philad.  1857,  p.  579),  and  Waters  (op.  cit.,  p.  159). 
According  to  the  latter  authority  it  is  best  seen  in  a  perfectly  fresh  spe- 
cimen of  lung  tissue,  and  by  the  aid  of  acetic  acid.  According  to  Kol- 
liker it  is  "  an  ordinary  pavement  epithelium  without  cilia,  which  forms 
a  single  layer,  and  rests  immediately  on  the  fibrous  coat"  of  the  pulmo- 
nary vesicles. — (Ed.) 


94  GLANDS. 

of  these,  the  deeper  layers  of  cells  are  many-sided,  and 
present  nothing  worthy  of  note ;  but  those  upon  the 
surface  are  conical,  with  their  bases  directed  towards 
the  axis  of  the  canal,  and  furnished  with  vibratile 
cilia  (PL  I.  fig.  VII.).  In  the  most  minute  bronchial 
tubes  the  deeper  strata  of  epithelial  cells  disappear 
entirely — the  ciliated  layer  alone  remaining. 

Underlying  the  epithelial  layer  we  have  the  mu- 
cous membrane,  consisting  of  a  delicate  web  of  inter- 
mingled connective  and  elastic  fibres.  These  latter 
have  a  longitudinal  direction,  and  occupy  the  outer 
aspect  of  the  membrane.  In  bronchise  of  some  size 
they  form  small  whitish  longitudinal  fasciculi,  per- 
fectly visible  to  the  naked  eye.  Outside  of  the  mu- 
cous membrane  we  have  a  layer  of  unstriped  mus- 
cular fibres,  circular  in  their  direction.  In  the  tra- 
chea, and  its  larger  subdivisions,  these  fibres  are  found 
only  in  their  posterior  aspect,  or  in  the  membranous 
portion  of  the  canal,  and  their  connexion  with  the 
extremities  of  the  cartilaginous  rings  has  been  demon- 
strated (Kolliker).  Here,  also,  longitudinal  muscular 
fasciculi  have  been  recognised,  occupying  the  outer 
aspect  of  the  circular  layer. 

Fibrous  coat.  Finally,  the  external  or  fibrous  coat  of  the  bron- 
chial tubes  is  formed  by  a  dense  interlacement  of 
connective  and  elastic  fibres.  It  contains  also  carti- 
laginous plates  of  variable  shape,  which  are  found 
only  upon  the  anterior  and  lateral  regions  of  the  tra- 
chea and  large  bronchi,  whilst  they  are  distributed 
upon  the  whole  circumference  of  the  smaller  canals. 
It  is  to  be  noticed  that  these  cartilaginous  lamellae 
become  smaller  and  less  frequent  in  proportion  as  the 


GLANDS.  95 

tubes  chminish  in  calibre,  and  finally,  when  this  has 
reached  a  diameter  of  one-half  of  a  line,  they  are  no 
longer  to  be  found.  Tubes  of  this  size,  in  fact,  consist 

O  I  ' 

simply  of  an  extremely  delicate  mucous  membrane, 
lined  externally  by  scattered  muscular  fibres,  and 
within,  by  ciliated  epithelium. 

Clusters  of  gland  vesicles  are  found  imbedded  in  Glands. 
the  thickness  of  the  walls  of  the  trachea  and  bronchi. 
Very  numerous  in  the  commencing  trunks  of  the  bron- 
chial tree,  they  become  less  and  less  frequent  as  its 
branches  diminish  in  size,  and,  according  to  Kolliker, 
are  no  longer  to  be  seen  in  bronchise  of  from  one  to 
one  and  a  half  lines  in  diameter.  These  little  glands, 
which  are  hardly  one-fourth  of  a  line  in  diameter,  are 
to  be  found  in  the  deepest  portion  of  the  mucous  coat 
of  the  tube,  or  rather  lying  upon  the  inner  surface  of 
its  fibrous  coat.  Their  epithelial  cells  are  polygonal, 
whilst  those  lining  their  ducts,  which  open  into  the 
bronchial  tubes,  are  cylindrical,  but  not  ciliated.* 

The  pleura,  like  the  other  serous  membranes,  are  Pleur*- 
not  very  complicated  in  their  structure.  They  are 
made  up  of  a  somewhat  dense  interlacement  of  fibres 
— connective  and  elastic — and,  upon  the  free  surface 
of  the  membrane  thus  formed,  a  simple  layer  of  pave- 
ment epitheliunl.  They  receive  numerous  blood- 

*  Waters  (op.  cit.  p.  122)  describes  two  sets  of  glands  as  belonging  to 
the  mucous  membrane  of  the  trachea  and  bronchial  tubes :  one  consisting 
of  simple  mucous  follicles,  found  everywhere  on  the  surface  of  the  mem- 
brane ;  the  other,  larger  in  size  and  compound  in  character,  found  only 
in  the  posterior,  or  membranous  portion  of  the  trachea  and  larger  bron- 
chial ramifications.  It  is  these  latter  which  are  supposed  to  furnish  the 
very  tenacious  and  viscid  masses  of  sputa  so  characteristic  of  certain 
stages  of  bronchitis. — (Ed.) 


96  GLANDS. 

vessels  from  a  variety  of  sources  (the  bronchial  and 
pulmonary  arteries,  intercostals  and  internal  mam- 
maries),  which  enter  at  their  attached  surfaces.  Fi- 
nally, nervous  filaments  have  been  traced  into  their 
substance  from  the  great  sympathetic,  the  nervus 
vagus,  and  the  phrenic  nerve. 

The  arteries  distributed  to  the  lungs  are  of  two 
sorts,  bronchial  and  pulmonary  arteries,  The  latter 
accompany  the  bronchial  tubes  to  their  terminal 
extremities,  and,  during  their  course,  subdivide  very 
frequently,  some  of  their  branches  going  to  the  small- 
est of  the  bronchise,  whilst  the  rest  terminate  on  the 
pulmonary  vesicles.  Before  they  finally  break  up 
into  a  capillary  plexus,  the  smaller  arterial  branches 
are  found  in  the  interstices  between  the  lobules  of  the 
lung,  where  they  anastomose  with  each  other  in  such 
a  manner  as  to  surround  each  lobule  with  a  vascular 
circle  or  network,  recalling  the  arrangement  of  the 
branches  of  the  vena  portce  around  the  lobules  of  the 
liver.  From  this  arterial  circle  branches  of  the  small- 
est size  are  given  off  in  great  number,  which,  by 
their  inosculations,  form  a  capillary  network  with 
exceedingly  small  meshes  (sioth  of  a  line  in  diameter), 
which  occupies  the  deep  layer  of  the  walls  of  the  pul- 
monary vesicles.  Of.  these  ultimate  branches  of  the 
pulmonary  artery,  some  leave  the  lobules  to  supply 
the  visceral  layer  of  the  pleura. 

veins.  The  radicles  of  the  pulmonary  veins,  which  take 
their  origin  from  the  capillary  plexus,  spread  them- 
selves upon  the  surface  of  the  pulmonary  vesicles, 
forming  a  stratum  more  superficial  than  the  capil- 
laries ;  then  they  lose  themselves  in  the  lobular  inter- 


GLANDS.  97 

slices,  where  they  unite  with  each  other  to  form 
larger  branches,  which  finish  their  course  afterwards, 
either  alone,  or  by  joining  company  with  branches  of 
the  pulmonary  artery. 

The  bronchial  arteries  supply  the  whole  bronchial  5™nchial  a 
tree,  and  also  the  pleurae.  Some  of  their  terminal 
branches,  those  which  supply  the  smallest  of  the 
bronchial  canals,  anastomose  with  branches  of  the 
pulmonary  arteries  and  veins ;  others  terminate  by 
corresponding  veinules*  through  which  their  blood  is 
ultimately  brought  back  to  the  vena  cava  superior.  Lymphatics 

The  lymphatics  of  lungs  form  two  sets,  one  of  which 
is  superficial,  ramifying  upon  the  pleurae,  and  the 
other  deep,  and  accompanying  the  bronchi  and  large 
vessels.  In  the  intervals  between  the  lobules  nume- 
rous anastomoses  take  place  between  these  two  sets 
of  vessels,  both  of  which  ultimately  reach  the  bron- 
chial glands  at  the  roots  of  the  lungs.  Lymphatic 
glands  have  never  as  yet  been  discovered  in  the 
parenchyma  of  the  lungs. 

The  nerves  of  the  lungs  are  derived  from  the  pneu-  Nerves. 

*  The  existence  of  bronchial  veins  within  the  lungs  is  denied  by  Wa- 
ters (op.  cit.),  whose  original  investigations  entitle  his  opinions  to  respect. 
At  p.  405,  under  the  head  of  bronchial  veins,  he  says,  "  The  only  vessels 
I  have  been  able  to  discover  to  which  this  name  can  be  applied,  are  some 
small  ones  situated  at  the  root  of  each  lung,  at  its  posterior  aspect.  I 
have  previously  mentioned  that  thgir  distribution  has  always  appeared  to 
me  to  be  confined  to  the  structures  about  the  root  of  the  lung,  the  bron- 
chi, the  bronchial  glands,  &c. ;  and  that  they  do  not  return  the  blood 
from  the  interior  of  the  lung.  I  have  never  seen,  either  in  the  lungs  of 
man,  or  those  of  other  mammalia  I  Jiave  examined,  any  veins  accompany 
the  several  branches  of  the  bronchial  artery  along  the  bronchial  tubes''1 
Keisseissen  (de  fab.  Pulmonum,  Berlin,  1823)  appears  to  hold  the  same 
view.— (Ed.) 


98  GLANDS. 

mogastric  and  the  great  sympathetic.  They  ramify 
in  company  with  the  bronchi  and  branches  of  the 
pulmonary  artery,  and  present,  at  intervals,  minute 
enlargements  composed  of  nerve  cells  ;  their  mode  of 
termination  is  unknown. 

Development.  According  to  M.  Coste*  the  first  appearance  of  the 
lungs  occurs  in  the  shape  of  a  small  granulation,  in 
the  median  line,  projecting  from  the  anterior  wall  of 
the  oesophagus.  This  little  mass  is  hollow  within,  and 
communicates  with  the  oesophagus  by  means  of  a 
vertical  slit  which,  eventually,  by  the  dilatation  of 
its  walls,  forms  the  larynx  and  trachea.  Soon  this 
central  mass  divides  into  two  lateral  portions  to  form 
the  two  lungs.  Still  later,  each  lateral  mass  divides 
itself  up  into  an  infinite  number  of  vesicular  vege- 
tations, and  is  thus  transformed  into  the  parenchyma 
of  the  lung.  Finally,  the  process  of  development  is 
completed  by  the  various  metamorphoses  of  the  em- 
bryonic cells  by  which  the  several  histological  ele- 
ments which  compose  the  tissue  of  the  respiratory 
organs  are  formed. 

According  to  Bischoff,f  and  most  of  the  German 
embryologists,  the  lungs  are  first  recognised  in  the 
form  of  solid  sprouting  buds,  which  subsequently 
become  hollow  by  the  melting  down  of  their  central 
cells  ;  the  remaining  steps  of  the  process  being  iden- 
tical with  those  already  described. 

gieabndTU8       Sebaceous  Glands. — Sebaceous  glands,  which  are 
almost  universally  associated  with  the  hair  follicles, 

*  Embryogenie  Compare'e.     Paris,  1837.— (Ed.) 
t  Professor  of  Physiology  in  the  t  University  of  Heidelberg,  Baden, 
Germany. — (Ed.)    • 


GLANDS.  99 

are  formed  by  a  duct,  which,  when  traced  from  its 
orifice,  is  found,  most  generally,  to  remain  undivided, 
and  to  terminate  in  a  solitary  bulb,  or  coecal  pouch, 
of  considerable  size  (PL  XVIII.  fig.  II.).  The  inter-  structure. 
nal  surface  of  this  pouch  is  covered  with  depressions, 
which  represent  the  vesicles  of  the  glands  we  have 
already  described.  Sometimes  a  group  of  these  de- 
pressions, becoming  deeper,  isolate  themselves  incom- 
pletely from  the  common  cavity,  by  a  partially 
formed  neck,  or  pedicle,  and  thus  constitute  a  lobule 
(fig.  III.  2).  The  wall  proper  of  the  sac,  or  pouch, 
is  structureless,  and  very  thin,  but  it  is  strengthened 
by  an  external  layer  of  fibrillated  tissue  (PL  XVIII. 
fig.  II.  5).  In  contact  with  its  inner  surface  are  one 
or  two  layers  of  young  cells,  with  finely  granular  and 
transparent  contents,  and  nuclei  which  are  quite  dis- 
tinct (fig.  II.  2).  Upon  this  epithelial  layer  are 
numerous  other  cells,  differing  from  those  just  de- 
scribed, both  in  volume,  and  in  their  contents.  They 
increase  in  size,  in  fact,  exactly  in  proportion  as  we 
trace  them  nearer  to  the  centre  of  the  gland  cavity ; 
and  during  their  growth  in  size,  the  nucleus  disap- 
pears, and  their  contents  are  transformed  into  oil- 
globules  (fig.  II.  1  ;  fig,  IV. ;  fig.  V.  2).  Finally,  near 
the  orifice  of  the  duct,  these  cells,  having  attained  the 
maximum  of  their  development,  and  being  no  longer 
able  to  resist  the  pressure  from  all  sides  of  the  cavity, 
the  contents  of  which  are  thus  constantly  increasing, 
rupture  their  cell  walls,  and  give  forth  a  sort  of  greasy 
substance  which,  in  short,  is  the  true  secretion  of  the 
sebaceous  gland  (PL  XVIII.  fig.  II.  4).  The  excre- 
tory canal  generally  opens  into  a  hair  follicle;  but 


100  GLANDS. 

sometimes  it  gives  directly  on  the  surface  of  the  skin, 
and  when  this  is  the  case,  that  portion  of  the  duct 
which  traverses  the  epidermis  has  no  walls  of  its  own 
(fig.  II  6). 

nores  and  ^e  vascular  supply  of  the  sebaceous  glands  pre- 
sents nothing  peculiar,  and  as  to  their  nerves  we 
know  nothing  of  their  distribution. 

Sebaceous  glands  are  developed  from  the  external 
epidermic  layer  of  the  hair  bulb,  or  rather  from  the 
rete  rmicosum  of  the  epidermis.  A  small  projection 
buds  forth,  on  the  surface  of  which  others,  still  small- 
er, make  their  appearance,  and  these,  increasing  in 
number,  constitute  the  vesicles  of  the  gland ;  whilst 
the  base  of  the  primitive  projection,  becoming  more 
elougated  and  constricted,  forms  its  duct.  According 
to  Valentin,  the  earliest  rudiments  of  the  sebaceous 
follicles  become  perceptible  during  the  last  half  of 
the  fourth  month  of  foatal  life. 

^e  Meibomian  follicles  are  an  aggregation  of 
minute  sebaceous  glands,  all  opening  into  a  long,  com- 
mon, excretory  duct  (PL  XXVII.  fig.  III.). 

The  mammary  gland,  which  in  external  appear- 
ance resembles  the  salivary  glands,  is  identical,  as 
regards  its  epithelium,  with  the  sebaceous  glands,  at 
least  during  lactation.  It  still  more  closely  approxi- 
mates to  the  sebaceous  glands  by  its  anatomical  posi- 
tion, and  its  mode  of  development. 

The  histological  elements  of  milk  consist  of  simple 
minute  oil-globules,  of  very  brilliant  aspect,  and  dark, 
strongly  marked  outlines,  floating  in  a  transparent 
fluid  (PI.  XVIII.  fig.  VI.  4).  During  the  first  few 
days  of  lactation  we  meet  with  a  certain  proportion 


GLANDS.  101 

of  these  oil-globules  which,  instead  of  being  free  and 
solitary,  are  aggregated  together  in  little  round  mass- 
es, forming  what  are  known  as  globules  of  colostrum 
(fig.  VI.  2).  When  the  gland  is  in  a  state  of  inflam- 
mation, these  colostrum  globules  make  their  appear- 
ance in  the  milk.  The  good  quality  of  the  milk  is 
known  by  the  large  number  and  equality  in  volume 
of  its  globules. 

On  reviewing  and  comparing  the  glands,  whose  Division  of 
structure  we  have  thus  far  studied,  reference  being 
had  solely  to  the  character  and  arrangement  of  their 
epithelium,  it  is  obvious  that  they  can  be  divided 
naturally,  into  two  groups :  1st,  glands  with  simple 
epithelium ;  2d,  glands  with  stratified  epithelium. 
In  each  of  these  varieties  the  process  of  secretion  is 
differently  accomplished.  In  the  first  group,  the 
plasma  of  the  blood  exudes  through  the  epithelial 
layer,  is  modified  by  its  cells,  and  passes  out  through 
the  excretory  duct  without  carrying  with  it  any  solid 
elements ;  this  is  the  process  of  secretion  by  -simple 
filtration.  In  the  second  group,  in  which  the  epi- 
thelial cells  are  packed  in  strata,  the  blood  plasma,  in 
passing  through  them,  excites  in  them  a  higher  grade 
of  vital  action ;  they  increase  rapidly  both  in  size  and 
number,  and  their  contents  undergo  at  the  same  time 
a  specific  change ;  but  both  the  cells  and  their  con- 
tents ultimately  become  disaggregated,  melt  down,  as 
it  were,  and  thus  form  the  secretion — which  is  hence 
called  secretion  by  epithelial  growth. 
;\  The  salivary  glands,  and  the  numerous  family  of 
mucous  follicles,  effect  their  secretion  by  the  mode 
first  described ;  the  sebaceous  glands,  and  the  mam- 


berknhn. 


102  GLANDS. 

mary  gland,  alone  belong  to  tlie  second  class.  We 
shall  see  hereafter  that  these  considerations  are  also 
equally  applicable  to  tubular  glands. 
of  Lie-  SECTION  2d.  TUBULAR  GLANDS.—  The  most  simple 
form  of  tubular  glands  are  those  of  Lieberkuhn, 
which,  as  is  well  known,  are  thickly  scattered 
throughout  the  whole  extent  of  both  the  small  and 
large  intestine.  They  are  simple  straight  tubes,  one 
end  of  which  opens  upon  the  free  surface  of  the  intes- 
tinal mucous  membrane,  whilst  the  other,  slightly 
enlarged  into  a  bulbous  sac,  is  imbedded  in  the 
deeper  portion  of  this  same  membrane  (PL  XXVI. 
fig.  X.).  Their  mean  diameter  varies  from  aVth  to 
aVth  of  a  line.  Each  follicle  is.  composed  of  a  struc- 
tureless basement  membrane,  on  the  outer  surface  of 
which  the  blood-vessels  belonging  to  the  intestinal 
glands  ramify,  whilst  within  it  is  lined  by  a  single 
layer  of  cylindrical  epithelial  cells,  which  are  arranged 
very  regularly  around  the  cavity  of  the  tube  (PL 
XXVI.  fig.  XI.  1,  2).  The  cavity  varies  from  lioth 
to  T^rth  of  a  line  in  diameter. 

Development.  The  development  of  these  glands  is  effected  at  the 
expense  of  the  epithelial  lamina  of  the  intestine, 
which  is  protruded  like  the  finger  of  a  glove  in  the 
form  of  a  tube.  They  will  be  hereafter  more  fully 
examined  in  connexion  with  the  intestinal  mucous 
membrane. 

The  glands  which  secrete  pepsin,  found  near  the 
cardiac  orifice  of  the  stomach,  and  its  mucous  follicles, 
situated  near  the  pylorus,  are  nothing  more  than 
compound  follicles  of  Lieberkuhn.  They  are  com- 
posed of  from  two  to  six  single  tubes,  siinilarlto  those 


GLANDS.     ;  103 

described  above,  which  unite  to  form  a  common 
excretory  duct.  In  the  mucous  glands  the  same 
variety  of  epithelium  lines  the  interior  of  the  tubes  of 
their  excretory  ducts ;  it  consists  of  conical  cells  simi- 
lar to  those  in  the  glands  of  Lieberkuhn,  measuring 
from  -sMla.  to  ^oth  of  a  line,  and  their  nuclei  4-Joth 
of  a  line  in  diameter  (PI.  XXV.  fig.  VIII).  The 
epithelium  of  the  ducts  of  the  pepsin  glands  is  similar 
to  this,  but  the  cells  of  their  tubes  are  larger  (yoo-th 
of  a  line),  and.  they  are  polygonal  in  shape  (PL 
XXVI.  fig.  1.).  Sometimes  they  present  minute  pro- 
jections of  the  basement  membrane  of  the  tubes,  so 
that  they  have  a  mamelonated  appearance  exter- 
nally. According  to  Kolliker,  the  epithelium  of 
these  compound  glands  is  liable  to  fatty  infiltration, 
a  phenomenon  which  we  never  observe  in  Lieber- 
kulm's  glands.  But  this  is  not  of  constant  occur- 
rence, and  it  is  probable  that  the  presence  or  absence 
of  fatty  particles  in  the  epithelium  of  these  glands, 
corresponds  to  periods  of  activity  and  rest  in  the 
functions  of  the  gastric  mucous  membrane. 

The  glands  of  the  mucous  membrane  of  the  uterus  uterine  glands. 
have  precisely  the  same  physiognomy  as  the  tubular 
gastric  glands.  Like  them,  they  consist  of  a  solitary 
tube,  or  of  two,  converging  to  a  common  excretory  duct, 
and  their  epithelium,  of  a  single  layer  of  conical  cells. 
As  most  of  them  are  too  long  to  be  accommodated  in 
the  thickness  of  the  mucous  membrane,  we  find  that 
their  local  extremities  are  somewhat  curved,  or  bent 
upon  themselves. 

The  glands  of  the  neck  of  the  uterus  are  not  so 
long  as  those  of  its  body.     When  their  orifices  be- 


104  .      GLANDS. 

come  obliterated,  their  secretion,  accumulating  within, 
distends  them  and  alters  their  shape,  so  that  they 
become  spherical,  and  thus  form  what  are  known  as 
the  Ovula  Nabothi. 

sweat  glands.       Sudoriparous  Glands. — These  tubular  glands  oc- 
cupy the  deepest  layers  of  the  skin  (PL  XXIII.  fig. 
I.  8).     The  body  of  the  gland,  or  glomerula,  is  a  little 
spheroidal  mass,  or  ball,  averaging  one-fourth  of  a  line  in 
diameter.  It  consists  of  a  tube,  rolled  and  twisted  upon 
itself,  and  terminating  by  a  blind  extremity,  which, 
in  rare  cases,  is  bifurcated  (PL  XIX.  fig.  IV).     Its 
walls  are  formed  by  an  extremely  thin  and  structure- 
less basement  membrane  (reVo-th  to  TaV^th  of  a  line  in 
diameter),  which  is  strengthened  externally  by  some 
fibres  of  connecting  tissue  very  rich  in  plasmatic  cells 
(fig.  IV.  4),  and  which  may  be  regarded  as  consti- 
tuting the  fibrous  envelope  of  the  gland.     The  inter- 
nal surface  of  the  tube  is  lined  by  a  single  layer  of 
pavement  epithelium,  whose  cells  measure  4<roth  of  a 
line  in  thickness  (fig.  VI.  2).     Finally,  the  glomerula 
is  surrounded  by  a   rich   vascular   network,  which 
affords  the  materials  for  its  secretion.     Of  the  mode 
of  innervation  of  these  glands  we  are  as  yet  ignorant. 
The  excretory  duct  of  a  sweat  gland,  after  leaving  the 
glomerula,  runs  directly  outwards  through  the  sub- 
stance of  the  skin,  towards  the  bottom  of  one  of  the 
furrows  upon  its  surface,   and  then,  traversing   the 
epidermis,  terminates  by  an  oblique  opening  upon  its 
outer  surface.     During  its  course  through  the  skin 
proper  it  is  perfectly  straight ;  but,  in  traversing  the 
epidermis,  it  turns  upon  itself,  forming  a  close  spiral 
twist  (PL  XXIII.  fig.  I.  9).     In  the  epidermis  the 


GLANDS.  105 

duct  has  no  proper  coat,  this  being  replaced  by  the 
epidermic  cells  which  form  its  walls,  but,  in  the  thick- 
ness of  the  skin,  its  walls  are  formed  by  two  coats : 
the  outer,  dense  and  fibrillated  (2 o oth  of  a  line  in 
thickness),  including  non-striated  muscular  fibres, 
which,  according  to  Kolliker,  are  also  found  in  the 
fibrous  envelope  of  the  glomerule ;  the  inner  coat  thin 
(Wo  <rth  of  a  line),  unorganized,  and  lined  by  an  epi- 
thelium similar  to  that  of  the  gland  (PL  XIX.  fig.  V. ; 
fig.  VI). 

The  ceruminous  glands,  which  belong  to  the  exter- 

nal  ear.  are  identical  in  form  with  the  sweat  glands : 

°  . 

they  differ  from  them  only  in  the  nature  and  arrange- 
ment of  their  epithelial  cells.  Thus,  instead  of  being 
spread  out  in  a  simple  layer  upon  the  internal  surface 
of  the  secreting  tube,  their  cells  form  a  series  of  strata 
by  which  its  cavity  is  completely  filled  (PL  XIX.  fig. 
VII.  2).  Moreover  they  become  infiltrated  with 
yellow  pigment,  and  oil-globules  in  abundance,  cha- 
racteristics in  which  these  glomerules,  as  regards  their 
secretion,  resemble  closely  the  sebaceous  glands.  The 
large  sudoriparous  glands  of  the  axillae  seem  to  be 
absolutely  of  the  same  species  a#  the  ceruminous 
glands,  for  their  contents  are  identical. 

The  sudoriparous  glands  are  developed  from  the  Development 
fifth  to  the  eighth  month  of  foetal  life.  They  make 
their  first  appearance  in  the  shape  of  minute  cellular 
projections  from  the  deep  surface  of  the  epidermis, 
which  imbed  themselves  in  the  true  skin.  At  first 
they  are  nothing  more  than  solid  cylinders  slightly 
bulbous  at  their  dermal  extremities.  As  they  grow, 
they  reach  the  deepest  layer  of  the  skin,  but  do  not 

7 


106  GLANDS. 

pass  beyond  its  limits;  as  their  growth  in  length, 
however,  goes  on,  they  curve  and  twist  upon  them- 
selves, so  as  to  form  the  glomeruli  which  we  find  in  the 
adult.  Whilst  these  changes  are  taking  place  in  the 
size  and  external  shape  of  the  sweat  glands,  their  inte- 
rior is  observed  to  become  converted  into  a  canal,  and 
this  is  probably  effected  by  the  disaggregation  and 
melting  down  of  the  central  cells.  Finally,  the  walls 
of  the  gland  tubes  are  perfected  by  a  series  of  morpho- 
logical transformations  of  the  more  superficial  cells  of 
the  original  cylinder. 

Preparations.  The  specimens  required  for  the  study  of  the  tubu- 
lar glands  are  very  readily  prepared.  It  is  simply 
necessary  to  detach,  by  means  of  scissors,  very  deli- 
cate little  lamellae  from  the  mucous  membrane  of  the 
intestine,  cutting  both  parallel  with,  and  at  right 
angles  to,  its  surface.  For  those  of  the  skin,  a  razor 
is  employed  in  the  same  manner,  and  dilute  solutions 
of  potassa  and  acetic  acid  are  applied  to  the  speci- 
mens in  order  to  render  the  tissues  more  trans- 
parent.* 

Kidneys,  struc-  Kidneys. — In  a  longitudinal  section  of  a  kidney, 
including  its  Tiilus,  the  parenchyma  of  the  gland  pre- 
sents itself  in  two  obviously  different  aspects ;  near 
the  liilus,  and  towards  the  centre  of  the  gland,  it  is 
striated ;  elsewhere  it  is  granular  in  appearance.  The 
striated  portion  (cones,  medullary  substance,  pyramids 
of  Malpighi)  consists  of  sections  of  cones,  of  which  the 

*  The  spiral  twist  of  the  duct  of  the  sweat  gland,  as  it  traverses  the 
epidermis,  is  best  seen  by  cutting  thin  slices  from  the  edge  of  a  piece 
of  dried  skin  of  the  palm  of  the  hand  or  sole  of  the  foot,  with  a  sharp 
scalpel.— (Ed.} 


tare. 


GLANDS.  107 

apices  (papilla)  converge  towards  the  liilus,  whilst 
their  bases  are  directed  outwards,  towards  the  surface 
of  the  organ.  The  granular  portion  (cortical  substance) 
forms  not  only  the  peripheral  substance  or  cortex  of 
the  organ,  surrounding  the  bases  of  the  pyramids, 
but  it  dips  inwards  between  them,  reaching  nearly  as 
far  as  their  summits.  The  free  surfaces  of  the  papillw 
are  pierced  by  numerous  small  orifices,  rVth  of  a  line 
in  diameter.  Each  of  these  orifices  leads  into  a 
straight  canal,  which,  in  its  course,  is  constantly 
dividing  and  subdividing,  always  into  two  branches, 
and  these  are  given  off  invariably  at  a  very  acute 
angle.  Having  reached  the  base  of  the  medullary 
cone,  all  of  these  subdivisions  of  the  primitive  tube, 
which  thus  far  have  pursued  a  perfectly  straight 
course,  immediately  become  exceedingly  tortuous, 
and  by  their  involutions  and  twistings,  form  the  cor- 
tical substance  of  the  gland,  each  tubule  terminating 
at  last  by  a  bulbous  extremity,  which  is  in  intimate 
contact  with  a  small  tuft  of  blood-vessels  called  a 
Malpighian  body  (PL  XX.  fig.  I.  2,  3). 

It  is  noticeable  that  the  line  which  limits  the 
base  of  each  pyramid  forms  a  series  of  indenta- 
tions, and  that  the  straight  tubes*  emerging  from 
the  summit  of  the  intervening  projections,  are  sur- 
rounded on  all  sides  by  tortuous  tubules  (fig. 

i.i). 

In  accordance  with  this  description  it  is  obvious 
that  each  primitive  straight  canal  gives  origin  to  a 
fasciculus  of  tubes  (pyramid  of  Ferrein,  lobule  of  the 
kidney)  which  pursue  a  straight  course  through  the 
substance  of  the  medullary  cones  (tubes  of  Bellini), 


108  GLANDS. 

and  become  tortuous  in  the  cortical  substance  of  the 
organ  (tubes  of  Ferrein). 

The  straight  tubes  measure,  on  an  average,  rVth  of  a 
line,  their  subdivisions,  jVth  of  a  line,  the  tortuous  tu- 
bules of  the  cortical  substance  aVth  of  a  line,  and  their 
bulbous  extremities  iVth  of  a  line.  A  perfectly  struc- 
tureless basement  membrane,  scarcely  Wo  oth  of  a  line 
in  thickness,  forms  the  outer  walls  of  these  secreting 
tubules,  which  is  hardly  distinguishable  except  when 
denuded  of  its  epithelium  (PL  XX.  fig.  II.  4).  Its 
internal  epithelial  lining,  at  least  ten  times  the  thick- 
ness of  the  outer  wall,  is  composed  of  a  single  layer 
of  many-sided  cells,  usually  pale  in  their  outlines,  and 
each  containing  a  large  and  well-marked  nucleus, 
which  is  very  clearly  recognisable  in  the  midst  of  its 
transparent  granular  contents  (fig.  II.  5,  7).  Fatty 
degeneration  of  these  epithelial  cells  is  the  principal 
lesion  of  the  urinary  tubules  in  Bright's  disease. 
These  two  membranes,  alone,  constitute  the  walls  of 
the  urinary  tubules,  as  far  as  their  bulbous  or 
expanded  terminations,  where  another  element  makes 
its  appearance,  which  we  shall  proceed  to  examine. 
Arteries.  In  the  hilus  of  the  kidney  the  renal  artery  divides 
into  about  a  dozen  branches,  which,  arranging  them- 
selves between  the  medullary  cones,  penetrate  the 
cortical  substance,  and  ultimately  reach  the  surface  of 
the  organ.  In  their  course,  which  is  almost  recti- 
linear, they  give  off  a  great  many  branches  to  the 
lobes,  as  they  traverse  the  spaces  between  them,  and 
some  smaller  arterioles,  also,  to  the  fibrous  envelope 
of  the  gland.  The  ultimate  branches  of  the  renal 
artery,  having  gained  the  interior  of  the  medullary 


GLANDS.  109 

pyramids,  shortly  after  their  origin,  pursue  a  course 
parallel  with  the  straight  tubes  of  which  they  are 
composed,  and  continue  onward  through  the  cortical 
substance,  towards  the  periphery  of  the  gland. 
Whilst  in  the  pyramids  there  is  nothing  peculiar  in 
their  distribution,  but,  as  soon  as  they  reach  the  cor- 
tical substance,  they  begin  to  give  off  small  branches, 
at  regular  intervals  (afferent  vessels),  in  every  direc- 
tion, which  penetrate  the  walls  of  the  secreting  tubuli, 
and  occupy  the  interior  of  their  expanded  extre- 
mities (PL  XX.  fig.  III.  1 ;  fig.  IV.  4,  5).  Here,  each 
afferent  vessel  breaks  up  into  a  certain  number  of 
branches,  which,  becoming  exceedingly  tortuous,  inter- 
twine with  each  other  so  as  to  form  a  little  round 
ball,  or  tuft,  which  is  known  as  the  Malpighian  body 
(glomerula  of  Malpighi,  corpus  MalpJiigianwii).  bSShian 

These  little  vascular  balls  completely  fill  the  pouch- 
like  terminal  expansions  of  the  tubuli  uriniferi,  and  it 
can  be  recognised  that  their  surfaces  are  entirely 
covered  by  a  layer  of  renal  epithelium.  We  have 
succeeded  in  demonstrating  this  relation  between  the 
Malpighian  tufts  and  the  epithelium  of  the  urinary 
tubules  on  several  occasions,  in  the  kidneys  of  the 
guinea-pig,  and  our  researches  into  the  structure  of 
the  human  kidney  have  led  to  the  same  result  (PI. 
XXVII.  fig.  IV.  5). 

A  solitary  vessel,  of  capillary  size  (the  efferent  Efferent  vessel, 
vessel),  leaves  the  Malpighian  tuft,  traversing  the 
wall  of  its  containing  cavity,  either  alone,  or  in  com- 
pany with  the  efferent  vessel,  near  which  it  is  always 
found;  it  immediately  divides  into  a  multitude  of 
ramifications,  which  anastomose  with  each  other,  and 


110  GLANDS. 

with  those  of  the  neighboring  efferent  vessels.  By 
this  system  of  anastomosing  vessels  the  capillary 
network  of  the  kidney  is  constituted,  and  the  urinary 
tubules  are  everywhere  closely  surrounded  by  it ;  in 
the  cortical  substance  this  network  is  very  fine  and 
close  (PL  XX.  fig.  III.  5),  but  in  the  medullary  cones, 
its  meshes  grow  longer,  and  the  number  of  the  vessels 
diminishes  (fig.  III.  6).  They  continue  to  diminish  in 
number,  and  to  increase  in  size,  forming  venous  radi- 
cles, which,  assuming  a  straight  course,  ultimately 
empty  into  the  renal  vein. 

Lymphatics.  The  origin  of  lymphatics  from  the  kidney  is  imper- 
fectly made  out,  and  the  same  is  true  of  the  termina- 
tions of  its  nerves,  which  enter  the  organ  at  its  hilus 
in  company  with  its  vessels. 

We  may  sum  up  the  structure  of  the  kidney  in  a 
few  words,  as  follows  :  from  a  papillary  orifice  a  canal 
takes  its  origin,  which,  leaving  its  sub-divisions  out  of 
view,  is  rectilinear  in  the  medullary  cones,  becomes 
tortuous  in  the  cortical  substance,  and  ends  there  in  a 
flask-like  pouch,  in  the  interior  of  which  the  Malpi- 
*  ghian  tuft  is  lodged.  This  takes  its  origin  from  one 
of  the  interlobular  arterial  branches  by  means  of  the 
afferent  vessel,  and  itself  gives  off  the  efferent  vessel, 
which  is  the  source  of  the  capillary  system  of  the 
organ,  by  which  its  secreting  tubules  are  enveloped, 
and  which  pours  its  blood  ultimately  into  the  renal 
vein.  The  secreting  tubules  have  two  walls  :  the  one 
thin  and  structureless,  the  other  much  thicker,  and 
consisting  of  a  layer  of  epithelial  cells  which,  at  its 
expanded  extremity,  are  found  covering  the  entire 
surface  of  the  Malpighian  tuft.  Nothing  certain  is 


GLANDS.  Ill 

known    of    its    nerves    and    lymphatics    (PL   XX. 
fig.  IV.). 

The  proper  coat  of  the  kidney  consists  of  a  dense  Fibrous  coat 
interlacement  of  connective  and  elastic  fibres  ;  its 
internal  surface  is  united  to  the  cortical  substance  of 
the  organ  by  minute  vessels,  and  delicate  trabeculse  of 
its  own  tissue  ;  its  outer  surface  is  continuous,  by 
means  of  slender  fibrous  processes,  with  the  mass  of 
adipose  tissue  in  which  the  gland  is  imbedded ;  at 
the  bottom  of  the  hilus  it  becomes  continuous  with 
the  calices. 

The  secreting  duct  of  the  kidney,  or  ureter,  is  ureter.  -\ 
expanded  above,  where  it  forms  the  pelvis  and  calices, 
and  terminates  below  at  the  bladder.  On  examining 
into  the  structure  of  its  walls,  we  find,  proceeding 
from  without  inwards:  1st,  a  fibrous  tunic;  2d,  a 
layer  of  smooth  muscular  fibres — composed  externally 
of  longitudinal  and  internally  of  circular  fasciculi ; 
3d,  a  mucous  membrane,  with  its  epithelium  in  strata, 
and  becoming  sensibly  thinner  where  it  passes  from 
the  surface  of  the  calices  upon  the  papillae.  Of  this 
epithelium  the  deep  cells  are  very  regularly  oval,  but 
those  nearer  the  surface  are  variable  both  in  size  and 
shape,  and  resemble  exactly  what  are  called  cancer 
cells ;  the  epithelium  of  the  bladder,  which  is  con- 
tinuous with  the  ureter,  presents  the  same  physi- 
ognomy; that  of  the  urethra  is  composed  of  cylin- 
drical and  oval  cells,  of  regular  form. 

In  the  unmixed  urine,  as  it  escapes  from  a  healthy  urine. 
kidney,  histologically,  there  is  nothing  to  be  recog- 
nised.    It  is  a  liquid  in  which  we  find  no  organized 
element,  unless  it  be  here  and  there  a  cell,  acciden- 


112  GLANDS. 

tally  detached  from  the  walls  of  tlie  ureters,  bladder, 
or  urethra,  and  carried  along  with  the  urine  in  the 
act  of  micturition. 

Development.  The  kidneys  are  developed  behind  the  "Wolffi  an 
bodies,  and  entirely  independently  of  them.  They 
take  their  origin  from  the  mucous  membrane  of  the 
intestine,  but  the  facts  which  we  possess  relative  to 
the  transformations  which  these  organs  undergo  dur- 
ing their  development,  are  not  clearly  enough  esta- 
blished to  justify  their  introduction  into  this  work. 

Preparations.  The  most  useful  preparations  for  the  study  of  the 
structure  of  the  kidneys,  are  sections  made  with  a 
razor  of  kidneys  rendered  solid  by  boiling,  and  simi- 
lar sections  of  fresh  organs,  as  well  as  of  those  previ- 
ously injected  with  fine  colors  ground  in  oil  and  well 
rubbed  up  with  pure  oil  of  turpentine. 

[The  most  recent  and  valuable  additions  to  our  knowledge  of  'the 
minute  structure  of  the  kidney  are  due  to  the  industry  and  talent  of 
the  late  Dr.  C.  E.  Isaacs.  His  admirable  paper,  entitled  "  Researches 
into  the  structure  and  physiology  of  the  kidney  (by  C.  E.  Isaacs, 
M.D.,  Demonstrator  of  Anatomy  in  the  University  of  the  City  of 
New  York,")  was  read  before  the  New  York  Academy  of  Medicine 
in  March,  1856,  and  in  its  numerous  and  excellent  illustrations  the 
student  will  find  great  assistance  in  thoroughly  comprehending  the 
minute  anatomy  of  this  organ. 

In  view  of  the  close  and  searching  investigations  of  Dr.  Isaacs 
into  the  doubtful  points  in  the  minute  structure  of  the  kidney,  and 
his  high  character  as  a  conscientious  and  skilful  observer,  I  feel  that 
no  apology  is  necessary  for  stating  his  conclusions  at  length,  and 
describing  the  ingenious  and  original  methods  by  which  he  arrived 
at  them. 

He  speaks  of  the  "  highly-elastic"  nature  of  the  basement  mem- 
brane forming  the  outer  wall  of  the  urinary  tubules,  and  adds,  "  the 
integrity  of  the  tube  being  of  the  highest  importance  during  life, 


GLANDS.  113 

this  membrane  has  been  endowed  with  the  quality  of  strongly  resist- 
ing injurious  influences,  and  even  powerful  chemical  reagents.  In 
virtue  of  this  last-named  property,  we  are  enabled  to  show  clearly 
the  tubes  of  the  kidney,  by  certain  processes  hereafter  to  be  de- 
scribed."— Trans.  N.  Y.  Acad.  of  Med.,  Vol.  I.  part  IX.  p.  379. 

In  relation  to  the  nature  of  the  renal  epithelium,  it  is  stated 
(p.  380)  that  "most  of  the  epithelial  cells  are  polygonal,  although 
many  are  oval,  and  others  of  a  rounded  or  irregularly  rounded 
shape."  .  .  .  "  It  is  extremely  difficult  to  meet  with  specimens  of 
the  kidney  sufficiently  healthy  to  exhibit  the  perfectly  normal 
epithelium."  ..."  The  epithelium  very  soon  becomes  changed 
from  decomposition,  or  by  the  action  of  water,  which  expands  the 
cells,  and  sometimes  causes  them  to  burst,  when  the  tubes  are  found 
to  contain  merely  nuclei  and  granular  matter.  In  examining  the 
epithelium,  it  is  therefore  very  important  to  obtain  the  kidney  in  as 
fresh  a  condition  as  possible,  and  instead  of  water,  to  use  a  solution 
of  albumen  in  water,  or  urine."  In  conclusion,  the  opinion  is 
expressed,  that  all  the  appearances  presented  by  the  renal  cells 
differing  from  the  characteristics  of  pavement,  or  tesselated  epithe- 
lium, are  the  result  either  of  decomposition  or  disease,  (p.  381.) 

As  to  the  presence  of  cilia  upon  the  epithelial  cells  of  the  kidney, 
it  is  admitted,  in  fishes  and  the  amphibia.  To  determine  the  ques- 
tion as  to  its  existence  in  the  mammalia,  he  "resorted  to  the  large 
establishments,  in  this  city,  for  killing  oxen,  sheep,  horses,  dogs, 
rats,  etc.,  and  examined  the  kidneys  immediately  after  the  death  of 
the  animal."  ..."  Some  of  the  scraped  substance  of  the  kidney 
was  gently  agitated,  in  a  test  tube,  containing  a  solution  of  albumen, 
and  a  drop  of  this  fluid  was  then  placed  under  the  microscope. 
Thin  sections  were  also  used.  In  some  animals  no  motion  could  be 
perceived,  but  in  the  dog  I  observed  currents  taking  place,  in  the 
fluid,  and  also  within  the  uriniferous  tubes.  The  epithelial  cells 
would  frequently  disengage  themselves  from  the  sides  of  the  tube, 
and  pass  along  for  a  considerable  distance,  and  after  emerging  from 
the  mouth  of  the  tube,  would  assume  a  rotatory  motion.  Sometimes 
nearly  all  the  epithelial  cells  would  pass  out  of  a  tube,  in  the  space 
of  fifteen  or  twenty  minutes,  leaving  it  almost  denuded  of  its  internal 
epithelial  lining.  I  have  also  seen  isolated  cells,  having  a  vibratory 
or  rotatory  movement.  These  appearances  I  have  noticed  upon 


114  GLANDF. 

eight  occasions,  in  the  kidneys  of  dogs.  Such  motions  generally 
cease,  in  these  animals,  in  less  than  an  hour  after  death.  .  .  . 
I  have  often  seen  appearances  similar  to  the  preceding,  in  the  kid- 
neys of  the  ox  and  sheep.  Nevertheless,  it  must  be  stated,  that  after 
very  numerous  and  careful  observations,  I  have  never  seen  the  epi- 
thelial cells  actually  provided  with  cilia,  except  upon  one  occasion, 
when  I  observed  a  single  cell  apparently  fringed  with  cilia,  and  in 
active  rotatory  motion.  This  was  in  the  kidney  of  the  ox."  .  .  . 
"  What  is  observed  in  the  kidneys  of  the  dog,  sheep,  and  ox,  cer- 
tainly seems  to  be  much  more  powerful  than  the  ciliary  motion  so 
readily  seen  in  the  oyster  *and  clam,  and  very  different  in  its  nature 
from  molecular  motion.  Reasoning  from  the  appearances  in  the 
oyster  and  clam,  as  well  as  from  analogy  in  many  of  the  lower 
animals,  it  may  be  concluded  that  ciliary  motion  does  exist  in  those 
of  a  higher  grade,  although  it  is,  in  them,  very  imperfect,  or,  as  it 
might  perhaps  be  said,  in  a  rudimentary  condition.  In  some  of  the 
inferior  animals,  where  the  urine  is  excreted  in  the  semi-fluid  state, 
a  much  greater  necessity  exists  that  this  fluid  should  be  rapidly  pro- 
pelled in  its  course  through  the  uriniferous  tu^es,  and,  accordingly, 
we  here  find  ciliary  motion  in  its  most  perfect  condition.  I  have 
never  seen  it  in  the  human  kidney,  even  after  many  careful  exami- 
nations. If  it  does  exist,  which  is  probable,  it  ceases  very  soon  after 
death,  when  it  rarely  happens  that  we  can  obtain  an  opportunity  of 
examining  it."  Kolliker,  in  the  last  edition  of  his  Manual  of 
Human  Microscopical  Anatomy,  Lond.  1860,  states  (p.  408)  that 
"it  (ciliary  motion)  is  absent  in  birds  and  mammalia,"  and  yet  he 
has  the  title  of  Dr.  Isaacs'  paper,  which  was  translated  into  Schmidt's 
Jahresber.  in  185Y,  enumerated  under  the  head  of  literature  of  the 
kidney.  So  that,  as  far  as  this  distinguished  histologist  is  concerned, 
Dr.  Isaacs'  observation  of  the  fact  of  the  existence  of  ciliary  motion 
in  the  uriniferous  tubes  of  the  kidney  in  mammalia,  is  original. 

In  regard  to  the  presence  of  epithelium  upon  the  surface  of  the 
Malpighian  tufts  of  the  kidney,  it  is  asserted  by  M.  Morel,  in  the 
text,  that  he  has  seen  it  on  several  occasions  in  the  kidneys  of  the 
guinea-pig,  and  also  in  man.  This  was  originally  asserted  by  Ger- 
lach,  but  is  doubted  by  Kolliker  (op.  cit.  p.  408),  and  denied  by 
Bowman  and  Dr.  G.  Johnson  (On  Diseases  of  the  Kidney,  Lond. 
1852,  p.  30,  note).  The  observations  of  Isaacs  upon  this  point  are 


GLANDS.  115 

conclusive,  as  will  appear  from  the  following  quotations  from  his 
paper.  I  will  add  also  that  I  have  myself  witnessed  several  undoubted 
demonstrations  of  the  fact  at  his  hands. 

"  After  much  reflection  as  to  the  best  plan  of  determining  this 
point,  I  adopted  the  following  processes :  1.  By  injecting  watery  and 
etherial  solutions  into  the  ureter,  I  succeeded  in  bursting  the  capsule, 
the  Malphighian  tuft,  or  coil,  having  been  previously  only  slightly 
and,  as  was  intended,  imperfectly  injected  from  the  artery.  Epi- 
thelial cells  could  then  be  seen  upon  the  uninjected  and  transparent 
edges  of  the  tuft,  or  coil.  Plate  24,  fig.  1,  exhibits  a  Malpighian 
tuft.  Broken  fragments  of  the  injected  vessels  are  seen  within  it. 
They  had  been  injected  with  chrome  yellow,  and  appear  black,  when 
the  specimen  is  viewed  by  transmitted  light.  The  uriniferous  tube 
had  been  distended  by  the  injection  from  the  ureter,  and  its  expanded 
extremity  or  capsule  had  been  burst,  and  can  be  perceived  lying 
in  shreds  at  the  sides  of  the  tuft,  now  uncovered  by  the  capsule. 
Nucleated  cells  can  be  seen  upon  the  naked  and  uninjected  parts  of 
the  tuft.  From  the  kidney  of  the  black  bear,  magnified  eighty  diame- 
ters." In  another  specimen,  the  capsule  had  been  scratched  off  with 
a  needle,  and  then  the  naked  tuft  somewhat  torn  under  the  micro- 
scope. Some  small  fragments  of  the  tuft  could  be  seen  with  nucle- 
ated cells  on  their  surface. 

Again  :  "  The  capsule  was  torn  off  from  a  Malpighian  body 
with  a  needle.  In  doing  this,  the  capsule  became  reversed,  so  as  to 
give  a  view  of  its  internal  surface,  upon  which  small  nucleated  cells 
could  be  clearly  and  distinctly  seen.  The  surface  of  the  naked  tuft 
was  covered  by  cells  of  much  larger  size  than  those  upon  the  interior 
of  the  capsule.  Upon  the  application  of  dilute  nitric  acid,  the  wall 
of  the  cells  of  the  capsule  was  dissolved,  while  comparatively  little 
effect  was  produced  upon  those  of  the  tuft,  thus  showing  a  difference 
in  their  chemical  constitution  and  organization?  This  specimen  was 
taken  from  the  kidney  of  the  racoon,  and  magnified  400  diameters. 

Again  :  "  Fine  scrapings  of  the  kidney  of  a  cat  were  agitated  occa- 
sionally for  two  or  three  days,  in  a  test  tube,  the  water  having  been 
frequently  changed.  By  this  method,  the  epithelial  cells  within  the 
capsule  were  washed  out,  so  that  the  space  thus  left  between  the 
tuft  and  the  capsule  became  filled  with  water,  which  had  soaked 
through  the  capsule.  By  slight  agitation,  while  the  specimen  was 


116  GLANDS. 

floating  in  the  water,  under  the  microscope,  it  could  be  rolled  over 
and  over,  so  as  to  show  various  points  of  the  surface  of  the  tuft, 
covered  by  nucleated  cells" 

"  By  the  different  processes  first  mentioned,"  he  concludes,  "  I 
consider  the  existence  of  nucleated  cells  upon  the  surface  of  the 
Malpighian  tuft,  and,  consequently,  its  analogy  with  the  other 
secreting  organs,  as  conclusively  demonstrated."  These  descriptions 
are  illustrated  by  several  highly  satisfactory  drawings,  pp.  404-407. 
The  modesty  of  the  author  prevented  him  from  emphasising  the  ori- 
ginality of  the  observation  contained  in  the  lines  in  italics,  which  were 
introduced  by  the  writer.  The  importance  of  the  anatomical  fact, 
thus  clearly  demonstrated,  that  the  Malpighian  bodies  of  the  kid- 
ney are  covered  by  an  epithelium,  the  cells  of  which  are  distinctly 
different  from  the  ordinary  epithelium  of  the  urinary  tubes,  can  be 
estimated  by  a  reference  to  the  fact  that  the  ingenious  and  almost 
universally  received  theory  of  the  action  of  the  kidney,  announced 
in  1842  by  Mr.  Bowman,  in  his  paper  in  the  Philosophical  Transac- 
tions, is  founded  mainly  on  the  belief  that  the  surface  of  the  vessels 
composing  the  Malpighian  tuft  were  naked  and  bare.  In  a  subse- 
quent paper  "  on  the  function  of  the  Malpighian  bodies  of  the  kid- 
ney" read  before  the  N.  Y.  Academy  of  Med.,  February  4th,  1857, 
its  ingenious  author,  by  a  series  of  novel  and  interesting  experiments, 
demonstrates,  satisfactorily,  that  the  function  of  the  Malpighian  tufts 
of  the  kidney  is  not  the  mere  separation  of  water  from  the  blood,  as 
Bowman  asserts,  and  that,  on  the  contrary,  it  separates  from  the 
blood  most  of  the  proximate  elements  of  the  urine,  any  element  of  the 
urine  which  is  not  secreted  by  the  Malpighian  tuft,  being,  probably, 
afterwards  separated  by  the  epithelial  lining  of  the  tubes.  Trans. 
N.  Y.  Academy  of  Med.,  Vol.  I.,  Part  IX.,  p.  452. 

Another  anatomical  point  settled  by  Isaacs  is,  that  the  ultimate 
ramifications  of  the  renal  artery  do  not  all  terminate  in  Malpighian 
tufts,  although  the  great  majority  of  them  do  so.  At  p.  385,  he 
gives  a  wood-cut  representing  a  small  branch  of  the  renal  artery,  as 
seen  under  the  microscope,  "  which  divides  into  two  twigs,  one  of 
which  supports  at  its  extremity  the  Malpighian  coil  or  tuft  of  capil- 
laries, whilst  the  other  enters  into  the  venous  plexus." 

He  also  confirms,  conclusively,  the  opinion  of  Bowman  as  to  the 
relation  existing  between  the  Malpighian  tufts  and  the  expanded 


GLANDS.  117 

extremities  of  the  convoluted  tubes  of  the  kidney,  demonstrating,  in 
opposition  to  the  statements  of  Toynbee,  Miiller,  Gerlach,  Bidder, 
and  others,  "that  the  convoluted  nriniferous  tubes  terminate  by 
forming  an  expanded  extremity,  or  capsule,  which  embraces  the 
Malpighian  tuft,  or  coil  of  capillaries." — (p.  401.) 

"  This  difference  of  opinion,  even  among  such  high  authorities, 
may  probably  be  accounted  for,  inasmuch  as  it  is  very  difficult,  by 
employing  the  usual  means  of  examination,  to  obtain  any  minute 
portion  of  the  organ  which  will  show  the  tube  connected  to  the 
Malpighian  body.  Moreover,  in  examining  any  thin  section  of  the 
kidney  (as  is  usually  done)  for  this  purpose,  it  is  to  be  remembered 
that  the  Malpighian  body  is  always  embraced  in  a  ring  of  the  fibrous 
matrix,  and  that  at  the  neck  of  the  tube,  or  its  commencement  of 
expansion  into  the  capsule,  is  its  weakest  part,  and  where  it  is  most 
easily,  and  indeed  almost  always,  torn  across,  especially  when  trac- 
tion is  made  upon  it,  as  is  usually  done,  in  tearing  out  the  specimen 
with  needles.  On  the  contrary,  by  using  scrapings  of  the  organ  (as 
recommended)  agitated  in  water,  which  softens  and  removes  many 
of  the  adhering  portions  of  the  matrix,  which  last  holds  and  confines 
the  Malpighian  body,  this  can  be  washed  out,  and  not  unfrequently 
with  the  convoluted  tube  attached  to  it."  (See  plates  15,  16,  19, 
20,  21,  and  22.)  p.  404. 

In  relation  to  the  'fibrous  matrix '  of  the  kidney,  mentioned  in 
the  last  quotation,  nothing  is  said  in  the  text.  It  is  the  more  impor- 
tant to  supply  the  omission,  as  this  histological  element  of  the  organ 
plays  a  most  important  part  in  many  of  its  diseased  conditions.  It 
was  first  described  by  Dr.  John  Goodsir,  Professor  of  Anatomy, 
Univ.  of  Edinburgh,  in  the  Monthly  Journal  of  Medical  Science, 
May,  1842  (see  also  Johnson  on  Diseases  of  the  Kidney,  Lond.  ]  852, 
pp.  16,  321).  Its  existence  has  been  doubted  by  some  high  authori- 
ties, but  the  demonstrations  contained  in  Dr.  Isaacs'  paper,  and  the 
numerous  views  which  he  gives  of  appearances  presented  under  the 
microscope  by  his  ingeniously  prepared  specimens,  place  all  doubt  at 
rest,  and  constitute  him  the  highest  authority  on  the  subject. 

The  following  quotations  contain  the  essential  points  which  he 
has  demonstrated ;  but  for  a  thorough  knowledge  of  the  subject,  a 
perusal  of  his  paper  with  its  admirable  illustrations  is  necessary. 
"  I  have  never  satisfactorily  succeeded  in  exhibiting  it  (the  matrix) 


118  GLANDS. 

by  following  the  directions  usually  given  for  this  purpose.  It  can, 
however,  be  always  easily  and  distinctly  shown  by  the  following 
process:  "Very  thin  slices  of  the  kidney  are  to  be  made  with 
Valentin's  knife,  put  into  a  long  test  tube  about  one  third  full  of 
water,  and  agitated  from  time  to  time  for  two  or  three  hours.  Pre- 
pared in  this  manner,  a  thin  section  exhibits  under  the  microscope  a 
kind  of  mesh,  network,  or  honeycomb  arrangement — the  cells  of  the 
honeycomb,  however,  having  no  bottom.  In  the  natural  condition 
of  the  kidney,  the  smaller  cells  or  openings  transmitted  the  tubes ; 
the  large  cells  or  openings  were  occupied  by  the  Malpighian  bodies; 
which  last,  together  with  the  tubes,  have  now  been  washed  out  of 
the  cells,  although  a  few  are  often  seen  still  remaining  in  situ,  pi. 
28."  Here  follow  representations  of  similar  preparations  from  the 
kidney  of  the  rat,  dog,  rabbit,  raccoon,  hog,  sheep,  ox,  horse,  elk, 
moose,  black  bear,  and  finally  of  the  human  kidney.  "  According 
to  my  experience,"  he  continues,  "  it  is  rare  to  find  a  human  kidney 
which  is  perfectly  healthy.  This  is  particularly  the  case  in  subjects 
in  the  dissecting  room,  and  in  those  who  have  died  in  large  hospi- 
tals. Out  of  more  than  500  subjects  which  I  have  examined  in  this 
city,  I  have  seen  but  very  few  in  which  the  kidney  could  be  regarded 
as  in  an  entirely  healthy  condition.  Being  very  anxious  to  procure 
a  perfectly  healthy  specimen  of  the  organ,  I  obtained  a  considerable 
number  of  kidneys  from  the  bodies  of  persons  killed  by  violence  and 
accidents,  but  these  were  also  found  to  be  diseased,  most  probably 
from  intemperance,  etc.  I  at  length  procured  the  healthy  organs 
from  which  the  present  view  of  the  matrix  is  here  given." 

"From  what  has  now  been  said  and  exhibited,  it  is  evident  that 
the  fibrous  matrix  is  really  the  skeleton,  or  frame-work  of  the  kid- 
ney. It  consists  of  myriads  of  septa,  or  partitions,  crossing  each 
other  in  various  directions,  so  as  to  form  elongated  spaces  for  the 
straight  tubes,  or  rounded  spaces,  cells,  or  rings,  for  the  Malpighian 
bodies  and  convoluted  tubes."  "  In  certain  pathological  conditions 
of  the  kidney,  it  becomes  diminished  in  size,  and  indurated  ;  its  sur- 
face is  irregular  and  covered  with  small  projecting  points,  like  vari- 
ously sized  shot.  This  condition  is  not  unfrequently  seen  in  old 
drunkards,  and  would  seem  to  be  analogous  to  cirrhosis  of  the  liver, 
and  probably  induced  in  a  similar  manner ;  the  alcoholic  fluid  passing 
through  the  tubes  of  the  kidney,  and  by  continued  irritation  pro- 


GLANDS.  119 

ducing  crisping,  or  irregular  contraction  of  the  meshes  of  the  matrix, 
which  consequently  constrict  the  tubes  and  the  Malpighian  bodies." 

"  Thickening  and  induration  of  the  matrix  may  produce  injurious 
effects  otherwise  than  by  constriction  of  the  tubes  and  Malpighian 
bodies.  The  minute  vessels  and  capillaries  pass  through  the  sub- 
stance of  the  fibrous  rings.  Consequently,  induration  and  contrac- 
tion of  the  matrix,  by  direct  pressure  on  the  vessels,  must  greatly 
interfere  with  the  circulation,  nutrition,  and  secretion  of  the  kidney, 
and  thus  various  morbid  products,  as  blood,  albumen,  pus,  tubular 
casts,  etc.,  may  be  found  in  the  urine."  Pp.  418-429.  By  isolation 
of  portions  of  the  matrix  by  repeated  washings,  and  the  subsequent 
application  of  dilute  acetic  acid  and  other  reagents,  it  was  found  to 
consist  entirely  of  fibres,  containing  elongated  fusiform  nuclei ;  in 
other  words,  to  be  pure  connective,  or  white  fibrous  tissue — the 
yellow  elastic  element  being  invariably  absent. 

"From  the  foregoing  remarks,  it  is  evident  that  a  correct  know- 
ledge of  the  fibrous  matrix  is  of  great  importance,  and  that  its 
microscopical  and  chemical  investigation,  in  all  cases  of  diseased 
kidney,  would  probably  furnish  interesting  and  valuable  results." 
P.  431. 

It  remains  to  notice  the  original  and  very  ingenious  methods  of 
preparing  the  specimens  by  means  of  which  Dr.  Isaacs  succeeded  in 
attaining  such  successful  results.  His  aim  was  to  render  the  sub- 
stance of  the  kidney  transparent  under  the  microscope,  and  to  effect 
this  he  instituted  numerous  experiments  with  chemical  reagents,  and 
"at  length  arrived  at  the  knowledge  of  certain  processes,  which 
have  not  only  been  useful  by  giving  transparency  to  small  portions 
and  thin  sections  of  the  organ,  but  have  often  enabled  them  to  be 
viewed  both  as  opaque  and  as  transparent  objects."  With  these 
processes,  all  the  usual  means,  such  as  injections,  etc.,  were  also 
employed.  The  following,  in  addition  to  those  already  indicated, 
are  the  modes  of  preparing  microscopical  objects  which  he  praises 
most  highly. 

To  show  the  epithelium  of  the  urinary  tubes;  their  sections,  or 
scrapings  of  the  kidney,  should  be  kept  in  a  solution  of  albumen  in 
fresh  urine.  "To  view  the  tubes  of  the  kidney  in  their  normal  con- 
dition very  thin  sections,  or  scrapings  of  the  cut  surface  of  the  organ, 
may  be  put  into  a  test-tube  with  water,  agitated  for  a  few  minutes, 


120  GLANDS. 

placed  on  a  slide  of  glass,  covered  by  a  thin  slip,  and  then  examined 
under  the  microscope."  Or,  to  render  the  object  transparent,  scrap- 
ings are  put  into  a  test-tube  with  about  half  an  ounce  of  water,  to 
which  three  drops  of  pure  sulphuric  acid  are  added,  and  the  whole 
boiled  for  one  or  two  minutes.  "  If  too  much  acid  be  used,  it  will 
dissolve  all  the  minute  vessels  and  capillaries,  but  not  the  Malpighian 
coil,  or  tuft.  This  is  worthy  of  notice,  as  showing  a  great  difference 
in  the  chemical  constitution,  and  consequently  in  the  organization, 
of  these  different  parts." 

The  addition  of  chloroform,  under  similar  circumstances,  also  has 
the  effect  of  rendering  objects  transparent.  "  I  have  succeeded  in 
exhibiting  the  tubes  of  the  kidney  very  distinctly,  by  boiling  small 
pieces  of  the  organ  in  diluted  chloroform,  and  also  in  solution  of 
chlorate  of  potassa,  which  latter  is  useful  in  giving  a  clear  view  of 
the  surface  of  the  kidney  when  congested,  as  it  shows  the  venous 
plexus  and  the  tubes,  and  acts  but  slowly  upon  the  blood-globules." 
To  show  the  vessels  in  connexion  with  the  Malpighian  bodies,  and 
at  the  same  time  to  exhibit  the  tubes  : — after  injecting  the  vessels 
with  white  lead  finely  ground  in  oil  (artists'  tubes),  and  well  agitated 
with  sulphuric  ether,  small  pieces  of  the  organ  were  boiled  in  very 
diluted  chloroform,  and  some  thin  sections  were  made  with  Valen- 
tin's knife  ;  other  sections  were  first  dried,  then  immersed  in  spirits 
of  turpentine,  and  finally  placed  on  a  glass  slide,  in  a  drop  of  water, 
under  the  microscope.  "  Muriatic,  acetic,  and  nitric  acids,  also  ex- 
hibit the  tubuli  with  considerable  distinctness;  the  last,  however,  is 
apt  to  discolor  the  tubes.  I  have  also  tried  the  effect  of  many  other 
chemical  reagents;  among  others,  the  phosphoric,  chromic,  boracic, 
tartaric,  and  citric  acids,  the  alkalies  and  their  carbonates,  various 
salts,  etc." 

In  conclusion,  I  must  again  urge  the  student  who  wishes  to  fully 
comprehend  the  anatomy  of  the  kidney,  to  consult  this  admirable 
paper,  and  study  its  graphic  illustrations ;  it  is  the  ablest  anatomical 
monograph  that  our  country  has  as  yet  produced,  and  a  fit  contribu- 
tion, by  its  lamented  author,  to  the  science  to  which  he  devoted  his 
life.]— (Ed.) 

Testicle.       Testicle. — The  proper  coat  of  the  testicle  (tunica 
albuginea)  is  of  the  same   structure  as  that  of  the 


GLANDS.  121 

kidney — but  somewhat  more  dense.  Its  external 
surface,  excluding  that  portion  corresponding  to  the 
hilus  of  the  organ,  is  clothed  with  a  simple  layer  of 
the  epithelium,  which  constitutes  the  visceral  ]amina 
of  the  serous  membrane  of  the  testis  (tunica  vagina-  structure. 
li$) ;  its  internal  surface  is  in  immediate  relation  with 
the  secreting  tubules  of  the  gland.  Along  the  line 
where  its  vessels  enter  and  leave  the  organ  (hilus)* 
the  tunica  alkuginea  presents  a  very  considerable 
thickening  (corpus  HigJimorianutri),  which,  in  the 
form  of  a  ridge,  buries  itself  in  the  parenchyma  of 
the  gland,  and  from  its  surface  the  interlobular 
fibrous  septa  take  their  origin.  In  the  interior  of  the 
corpus  Highmorianum  is  a  tubular  network  (rete  tes~ 
tis),  from  which  the  secreting  tubules  are  given  off  on 
one  side,  and  from  the  other,  the  efferent  canals  which 
terminate  in  the  excretory  duct. 

From  the  interior  of  the  rete  testis  twenty  to  thirty  vasa  recta, 
straight  tubes,  rVth  of  a  line  in  their  mean  diameter, 
take  their  origin  (vasa  recta),  and,  after  a  short 
course,  divide  into  several  branches.  Each  one  of 
them  becomes  exceedingly  tortuous  (PI.  XXL  fig.  I), 
and  again  gives  off  several  subdivisions,  which  anasto- 
mose with  each  other,  and  terminate  either  by  loops, 
or  by  blind  extremities.  Sometimes  one  of  these 
branches,  but  more  frequently  two  or  three  of  them 
closely  united,  form  a  lobule  of  a  conical  shape,  the 
apex  of  which  is  in  relation  with  the  rasa  recta,  whilst 
its  base  looks  towards  the  periphery  of  the  organ. 
Not  unfrequently  canals  of  communication  exist  be- 
tween these  lobules. 

The  upper  extremity  of  the  rete:  testis  gives  off  a  Efferent  tubes. 

8 


122  GLANDS. 

dozen  tubuli  (vasa  efferentid)  which,  by  their  union, 
constitute  the  head  of  the  epidydimis  (cjlobus  major). 
Immediately  after  emerging  from  the  corpus  HigJimo- 
rianum  these  tubes  become  exceedingly  convoluted, 
and  proceed  in  succession  to  the  globus  major  of  the 
epidydimis ;  each  of  them  takes  the  shape  of  a  cone 
(coni  vasculosi),  the  apex  of  which  is  continuous  with 
the  rete  testis.  Finally,  the  canal  of  the  epidydimis, 
after  having  by  its  convolutions  formed  the  body  of 
the  epidydimis  and  its  lower  extremity  (c/lobus  mi- 
nor), and  after  giving  off  the  vasculum  aberrant,  be- 
comes the  vas  deferens,  or  excretory  duct  of  the 
gland. 

Tubuii testis.  The  spermatic  tubules  (tubuli  testis)  and  the  vasa 
recta,  which  are  directly  continuous  with  them,  have 
very  thick  walls,  consisting  of  several  distinct  layers. 
The  external,  which  is  the  thickest  (zioth  of  a  line), 
is  fibrous  and  very  rich  in  plasniatic  cells  (PL  XXI. 
fig.  II.  1)  ;  the  internal,  exceedingly  thin  and  struc- 
tureless (fig.  II.  2),  is  in  relation,  by  its  inner  surface, 
with  the  stratified  epithelium  by  which  the  cavity  of 
the  tubule  is  completely  filled  (fig.  IL  3).  The  cells 
of  this  epithelium  are  of  considerable  size,  polyhe- 
dral, and,  in  the  adult,  most  of  them  contain  oil- 
globules.  In  the  rete  testis  the  tubuli  have  no  pro- 
per walls ;  they  are  simply  tunnels  through  the  fibrous 
substance  of  which  the  corpus  Highrnorianum  is  com- 
posed. 

^id/eferen8.and  ^n  the  epidydimis  the  non-striated  muscular  ele- 
ment is  added  to  those  already  recognised  in  the 
walls  of  the  tube,  and  its  epithelium  is  cylindrical 
(PI.  XXI.  fig.  III.).  The  vas  deferens,  proceeding  from 


GLANDS.  123 

without  inwardly,  is  composed :  1st.  of  a  fibrous  coat ; 
2d.  of  a  muscular  coat,  with  both  longitudinal  and 
circular  fibres  ;  3d.  of  a  mucous  coat,  lined  by  simple 
pavement  epithelium.  The  vesiculce  seminales,  with 
the  exception  that  their  walls  are  thinner,  possess  the 
same  structure  as  the  vas  deferens. 

The  arteries  of  the  testes,  ramifying  in  the  inter-  ^8aiMi 
lobular  septa,  terminate  in  a  capillary  plexus  which 
surrounds  the  tubuli  seininiferi.  The  veins  follow 
the  course  of  the*  arteries.  The  lymphatics  are  very 
numerous ;  they  accompany  the  vessels  of  the  cord, 
and  run  into  the  lumbar  glands.  The  nerves,  few  in 
number,  follow  its  arteries  into  the  parenchyma  of  the 
gland,  but  how  they  terminate  there  is  not  known. 

The  -semen  is  an  alkaline  liquid,  destitute  of  color,  seminal  fluid. 
in  which  certain  accessory  elements  are  encountered, 
such  as  cells  and  the  debris  of  cells,  and  also  certain 
essential  and  characteristic  elements — the  filiform  cor- 
puscles endowed  with  the  power  of  motion,  and 
known  under  the  name  of  spermatozoa.  These 
curious  corpuscles  consist  of  exceedingly  delicate  fila- 
ments with  an  almond-shaped  enlargement  at  one 
extremity,  constituting  its  head,  whilst  the  remainder 
of  the  filament,  tapering  off  to  an  extremely  fine 
point,  represents  the  tail.  A  delicate  linear  depres- 
sion, or  species  of  collar,  marks  the  line  of  junction 
of  these  two  portions,  on  the  borders  of  which  a 
minute  tubercular  projection  is  sometimes  to  be  seen 
(PL  XXI.  fig.  IV.).  No  trace  of  organization  can 
be  detected,  on  the  closest  examination,  in  any  part 
of  the  spermatozoa ;  the  substance  of  which  it  is 
composed  being  homogeneous,  transparent,  and  amor- 


124  GLANDS. 

phous.  The  movements  of  the  spermatozoa  con- 
tinue a  long  time  after  death  (10  to  24  hours) ; 
water  and  acids  arrest  them,  but  they  are  renewed 
again  by  the  application  of  slightly  alkaline  liquids. 
of  These  elements,  which  constitute  the  essential  por- 
tion of  the  seminal  secretion,  are  developed  in  the 
following  manner :  On  examining  the  epithelium  of 
the  tubuli  seminiferi  it  is  observed  that  its  central 
cells  are  generally  more  voluminous  than  the  rest, 
and  give  evidence  of  a  more  or  less  active  process  of 
endogenous  vegetation  (PL  XXL  fig.  V.)  ;  thus,  some 
cells  are  to  be  seen  enclosing  as  many  as  ten  nuclei. 
In  addition  to  the  nucleolus,  which  is  visible  in  each 
nucleus,  in  the  shape  of  a  brilliant  spherical  vesicle, 
there  is  also  observable  upon  one  point  of.  its  peri- 
phery an  elongated  spot  (fig.  V.  3),  from  which  shortly 
a  long  and  delicate  filament  takes  its  origin,  which 
coils,  upon  itself  as  it  increases  in  size,  occupying 
always  the  periphery  of  the  nucleus  (fig.  V.  7).  As 
soon  as  the  nuclei  have  attained  their  full  develop- 
ment, the  parent  cell,  being  no  longer  able  to  contain 
them,  bursts,  and  they  thus  become  free.  Its  ele- 
ments subsequently  become  disintegrated  and  disap- 
pear. The  tail  of  the  spermatozoon  then  uncoils  itself 
(fig.  V.  8),  afterwards  its  head  becomes  disentangled, 
and  its  development  is  accomplished. 

In  the  testes  of  the  guinea-pig,  we  have,  on  several 
occasions,  traced  the  successive  transformations  which 
the  epithelial  cell  undergoes  in  giving  origin  to  sperma- 
tozoa, and  have  always  witnessed  the  occurrence  of  the 
phenomena  taking  place  as  above  described ;  that  is, 
each  nucleus  distinctly  gives  origin  to  a  spermatozoon. 


GLANDS.  125 

In  the  human  testis  the  same  process  has  been  demon- 
strated. 

The  testicle  is  developed  from  the  internal  sub- 
stance  of  the  Wolffian  body,  whilst  its  excretory  duct 
is  formed  by  the  external  canal  of  the  same  organ 
The  vas  aberrant  takes  its  origin  from  the  centre  of 
the  Wolffian  body,  from  which,  according  to  some 
authorities,  the  epidydimis  also  is  formed.  The  his- 
tological  changes  which  take  place  during  the  deve- 
lopment of  the  testicle  are  not  demonstrable  with 
sufficient  certainty  to  justify  their  formal  description. 

What  has  been  said  already  in  reference  to  the 
epithelium,  and  mode  of  secretion,  of  glands  composed 
of  clusters  of  follicles,  applies  with  equal  force  to 
those  composed  of  tubes.  Those  which  possess  a 
single  layer  of  epithelium,  and  in  which  secretion  is 
effected  by  simple  filtration,  are :  the  glands  of  the 
intestinal  canal,  those  of  the  uterus,  the  sweat  glands, 
the  kidneys,  and  the  liver. 

The  glands  which  have  a  stratified  epithelium,  and 
in  which  secretion  is  effected  by  vegetation  of  its 
cells,  are  the  ceruminous  glands,  and  the  testicles. 

SECT.  III.  MIXED  GLANDS. — The  ovary  in  some 
respects  resembles  the  blood-glands,  but  differs  from 
them  by  possessing  an  excretory  canal,  and  by  the 
peculiar  character  of  its  follicles ;  the  liver,  with  its 
double  apparatus  for  the  secretion  of  bile  and  sugar, 
is  both  a  tubular  and  a  blood-gland.  The  structure 
of  these  two  organs  makes  it  necessary,  therefore,  to 
associate  them  together  in  a  separate  group,  which 
constitutes  naturally  a  connecting  link  between  the 
true  and  blood-glands. 


126  GLANDS. 

ovary  structure.  The  Ovary.  The  envelope  of  the  ovary  (tunica 
albugined)  is  of  the  same  nature  as  that  of  the  testi- 
cle, and  like  it,  is  covered  everywhere,  except  at  its 
lower  border  (hilus),  by  a  serous  membrane.  Its 
inner  surface  is  intimately  adherent  to,  and  continu- 
ous with  the  parenchyma  of  the  organ.  This  is  com- 
posed of  an  obscurely  fibrous  substance,  traversed  by 
numerous  blood-vessels,  in  the  meshes  of  which  the 
ovisacs,  or  Graafian  vesicles  are  found.  At  the  lower 
border  of  the  ovary  its  fibrous  element  is  denser  than 
elsewhere,  and  forms,  with  the  tunica  albuginea,  a 
sort  of  corpus  Highmorianum,  in  which  there  are  no 
ovisacs  ;  but  just  outside  of  it,  and  throughout  the 
whole  parenchyma  to  its  outer  surface,  large  numbers 
of  them  exist,  and  of  all  dimensions — the  larger  ones 
always  lying  nearest  to  the  surface  of  the  organ. 

The  outer  envelope  of  the  ovisac  is  a  fibro-vascular 
membrane  consisting  of  the  same  material  as  the 
parenchyma  in  which  it  is  embedded,  only  more  con- 
densed. The  external  portion  of  this  membrane, 
which  is  loosely  adherent  to  the  surrounding  tissue, 
is  less  vascular  than  its  deeper  surface.  In  contact 
with  this  is  a  stratified  epithelium  (inenibrana  granu- 
losa),  which  increases  considerably  in  thickness  near 
the  point  which  looks  towards  the  surface  of  the 
ovary,  and  constitutes  the  proligerous  disc,  in  the 
interior  of  which  the  ovule  or  egg  is  contained  (PL 
XXI.  fig.  VI.  2,  3,  4).  The  remaining  cavity  of  the 
ovisac  is  filled  by  an  albuminous  fluid  which  contains 
cells,  or  the  debris  of  cells,  detached  from  the  mem- 
brana  granulosa. 

The  proper  tunic  of  the  ovule  (vitelline  membrane, 


GLANDS.  127 


zona  pellucida)  is  about  ^th  of  a  line  in  thickness, 
transparent,  and  entirely  structureless.  Its  contents, 
the  vitellus  or  yelk,  scarcely  liquid  in  consistence, 
contains  a  great  number  of  very  fine  granules,  pro- 
bably fatty  in  their  nature.  At  one  point  of  the 
periphery  of  the  vitellus  there  is  a  brilliant  spherical 
nucleus,  the  germinal  vehicle,  or  vesicle  of  Purkinje.* 
Finally,  the  nucleus  itself  contains  a  nucleolus,  called 
the  germinal  spot  (  Wagner).  f 

Generally,  as  is  well  known,  the  ovisac  contains  but 
one  ovule  ;  nevertheless,  it  may  contain  two,  as  we 
have  seen  in  one  instance,  in  the  ovary  of  an  adult  (PL 
XXI.  fig.  VII.  1,  2).  We  have  also  observed  an 
example  of  segmentation  of  the  vitellus  in  another 
ovum  of  the  same  female,  which  proves  that  this  phe- 
nomenon may  take  place  in  the  interior  of  the  ovary 
without  previous  fecundation  (fig.  VIII). 

The  Fallopian  tube,  or  oviduct,  which  serves  as  the  raiiopian  tube. 
excretory  duet  of  the  ovary  after  the  detachment  of 
the  ovum,  has  three  layers  of  tissue  in  its  walls  ;  the 
first  is  serous,  and  belongs  to  the  peritonaeum;  the 
next  is  composed  of  smooth  muscular  fibres  and 
blood-vessels  ;  the  third  is  mucous  membrane,  the 
surface  of  which  presents  longitudinal  plaits,  and  is 
covered  by  a  single  layer  of  cylindrical  ciliated  epi- 
thelium. The  vibratory  motion  of  the  cilia  tends  to 
carry  the  contents  of  the  tube  onwards  from  without 
inwards,  and  consequently  facilitates  the  descent  of 
the  ovum  towards  the  cavity  of  the  uterus. 

*  Purkinje,  Professor  of  Physiology  in  the  University  of  Prague.  —  (Ed.) 
t  Rudolf  Wagner  lately  resigned  the  Chair  of  Physiology  at  the  Uni- 
versity of  Gottingen,  and  was  succeeded  by  Meissner.  —  (Ed) 


128 


GLANDS. 


The  uterus,  into  which  the  ovum  passes  from  the 
Fallopian  tube,  possesses  the  same  tissues  in  its  walls, 
only  the  second,  or  muscular  coat,  is  much  more 
developed  than  in  the  oviduct,  especially  during  ges- 
tation. Its  third,  or  mucous  lining,  is  also  more  com- 
plicated in  its  structure ;  the  portion  of  it  which 
belongs  to  the  body  of  the  organ  resembles  that  of 
the  Fallopian  tube,  but  that  which  lines  its  neck  is 
studded  with  filiform  papillae  which  overlap  each 
other ;  they  are  found  near  its  inferior  orifice ;  in 
addition,  we  have,  in  the  mucous  lining  of  the  uterus, 
large  numbers  of  tubular  glands,  which  have  already 
been  described. 

The  vagina  has  also  three  coats :  the  outer,  fibrous ; 
the  middle,  musculo-vascular ;  and  internal,  mucous. 
On  the  latter  we  find  numerous  deep  rugae,  especially 
towards  its  orifice,  and  a  large  number  of  conical 
papillae.  Its  epithelium  is  thick  and  stratified.  Thus 
far  no  glands  have  been  found  in  the  thickness  of  its 
walls. 

and  The  arteries  of  the  ovary  enter  that  organ  at  its 
lower  border,  and  break  up  into  a  great  many  very 
tortuous  branches,  of  which  some  are  distributed  to 
its  parenchyma  and  fibrous  envelope,  whilst  the  rest 
go  to  form  a  close  capillary  plexus  in  the  walls  of  the 
ovisacs.  Its  veins  follow  the  track  of  the  arteries, 
and  terminate  in  the  ovarian  and  uterine  veins.  Its 
lymphatics,  whose  origin  is  not  fairly  made  out, 
accompany  the  blood-vessels,  and  finally  communicate 
with  the  pelvic  and  lumbar  glands.  As  to  its  nerves, 
they  run  with  its  arteries  into  the  secreting  portion 
of  the  organ,  but  their  distribution  and  mode  of  ter- 
mination are  unknown. 


GLANDS.  129 

The  ovary  is  developed  at  the  expense  of  the  inte-  Development, 
rior  substance  of  the  Wolffian  body,  and  is  distin- 
guishable -from  a  testicle,  by  not  being  continuous 
with  its  excretory  duct.  It  consists,  at  first,  exclu- 
sively of  embryonic  cells,  the  greater  part  of  which 
are  transformed  into  the  ovisacs ;  the  remainder  form 
the  parenchyma  and  envelope  of  the  organ.  In  the 
ovaries  of  the  foetus,  or  newly  born  infant,  the  ovi- 
sacs are  readily  recognised  as  a  series  of  pockets  lined 
internally  by  a  layer  of  epithelial  cells  which  sur- 
round another  larger  central  cell;  this  eventually 
becomes  the  ovula,  whilst  those  which  surround  it, 
increasing  in  number,  form  the  membrana  granulosa, 
and  proligerous  disc. 

The  body  of  Rosenmuller,  or  parovarium,  situated 
between  the  layers  of  peritonaeum  which  connect  the 
ovary  and  fimbriated  extremity  of  the  Fallopian  tube, 
and  consisting  of  a  number  of  blind  canals,  represents 
the  remains  of  the  central  portion  of  the  Wolffian 
body,  and  corresponds  to  the  vasculum  dberrans  in 
the  male. 

The  liver  is  covered  externally,  on  all  sides,  by  a  LlTer- 
layer  of  connecting  tissue  which,  at  its  transverse  fis- 
sure, applies  itself  to  the  vessels  of  the  organ,  and 
following  them  into  its  parenchyma,  accompanies 
them  in  their  ramifications,  forming  a  common  invest- 
ment for  them,  and  the  whole  organ,  which  is  known 
as  the  capsule  of  Glisson. 

The  outer  surface  of  this  proper  coat  of  the  liver  is 
very  closely  united  to  the  peritonaeum  throughout  its 
whole  extent,  except  at  its  posterior  border,  its  trans- 
verse fissure,  and  at  the  fissure  for  the  gall-bladder. 


130  GLANDS. 

Its  internal  surface  sends  innumerable  delicate  pro- 
cesses, or  trabeculse,  into  the  interior  of  the  organ, 
which  traverse  its  parenchyma, '  and  become  ulti- 
mately continuous  with  the  connecting  tissue  which 
accompanies  its  vessels  to  their  extreme  ramifications. 

The  parenchyma  of  the  gland  consists  of  an  aggre- 
gation of  little  granules,  one-fourth  to  one- half  of  a 
line  in  diameter,  of  a  yellowish-brown  color,  and 
darker  centrally  than  on  the  surface.  This  color 
varies  considerably,  for  it  depends  upon  the  amount 
of  blood  in  the  ramifications  of  the  portal  vein,  and 
in  those  of  the  hepatic  vein,  and  also  upon  the  degree 
of  fatty  infiltration  which  exists  in  the  hepatic  cells. 
In  the  human  liver  the  outlines  of  these  granules, 
called  also  acini  or  lobules,  are  rather  indistinct ; 
but  in  the  hog  it  is  different ;  here  each  lobule  forms 
a  little  polygon,  entirely  independent  of  its  neighbors, 
and  presenting  a  very  distinct  outline. 

Each  lobule  of  the  liver  represents,  in  its  structure, 
a  miniature  of  the  whole  organ ;  it  will  suffice  there- 
fore to  study  one  of  them  thoroughly,  in  order  to  get 
an  exact  idea  of  the  histology  of  the  gland.  In  each 
lobule  we  find :  1st,  a  mass  of  hepatic  cells ;  2d,  the 
terminal  ramifications  of  the  venae  portae  and  of  the 
hepatic  veins ;  3d,  the  biliary  apparatus,  consisting  of 
the  radicles  of  the  hepatic  duct,  and  the  terminal 
branches  of  the  hepatic  artery. 

The  cells  are  of  two  sorts :  the  one,  which  consti- 
tutes pretty  much  the  whole  epithelial  mass,  are  large 
and  irregular  polygons,  jVth  of  a  line  in  diameter, 
with  nuclei  almost  always  infiltrated  with  fat,  and 
contents  consisting  of  free  oil-globules,  and  a  large 


GLAWDS.  1 31 

quantity  of  minute  pale  granules,  which  Sehiff* 
regards  as  a  species  of  animal  starch  (PL  XXII.  fig. 
IV.  1).  The  other  cells,  much  smaller  (^th  of  a 
line)  and  less  numerous,  have  a  regular  polygonal 
form,  and  finely  granular  contents,  generally  free  from 
fat  (fig.  IV.  2).  In  the  interlobular  spaces,  which  in 
the  hog's  liver  are  very 'distinct,  we  find  minute 
branches  of  the  venae  portee  (interlobular  veins),  by 
which  the  lobules  between  which  they  are  situated 
are  supplied  with  blood  (PL  XXII.  fig.  I.  2,  3).  If 
we  examine  closely  the  relations  between  the  inter- 
lobular veins  and  a  single  lobule,  we  find  them  form- 
ing around  it  a  vascular  network,  from  the  concavity 
of  which  a  multitude  of  minute  ramusculi  take  their 
origin,  which  penetrate  the  substance  of  the  lobule, 
and  immediately  break  up  into  capillaries  (fig.  I.  4 ; 
fig.  II.  2).  They  anastomose  freely  with  each  other, 
and  thus  form  a  network  with  very  close  meshes 
(^oth  of  a  line),  which  empties,  finally,  at  the  centre 
of  the  lobule,  into  a  minute  veinule,  which  is  a  radi- 
cle of  the  sub-lobular  hepatic  vein  (fig.  III.  2).  In 
man,  the  lobules  not  being  clearly  limited  in  their 
outlines,  the  vascular  circle  thus  formed  by  the  penul- 
timate branches  of  the  portal  vein  is  not  readily  dis- 
tinguished, but  the  capillary  network  in  their  interior 
has  the  same  appearance  and  arrangement  as  that 
described  (fig.  IL). 

The  large  hepatic  cells,  usually  connected  to  each 
other  in  pairs,  fill  up  the  meshes  of  the  capillary 
plexus  of  the  lobule,  and  in  their  aggregate  mas&  con- 

*  Professor  of  Physiology  in  the  University  of  Zurich. — (Ed.) 


132  GLANDS. 

stitute  an  epithelial  network,  which  is  interwoven  thus 
with  the  web  of  capillary  vessels.  The  elements  of 
the  liver  which  we  have  studied  thus  far  constitute 
its  glycogenous  apparatus. 

Hepatic  duct.  The  hepatic  duct  enters  the  liver  at  its  transverse 
fissure  along  with  the  hepatic  artery  and  portal  vein, 
and  accompanies  these  vessels  to  the  lobules.  In  its 
course  it  gives  off  a  great  many  arborescent  branches, 
of  which  the  larger  anastomose  frequently  with  each 
other,  whilst  the  smaller  ones  remain  solitary  and 
continue  on  to  the  surfaces  of  the  lobules.  From 
these  minute  perilobular  ramifications  arises  a  set  of 
capillary  tubes  which  enter  the  substance  of  the 
lobules — not  very  deeply — and  there  terminate  in 
blind  extremities  ;  they  are  lined  within  by  a  simple 
epithelial  layer,  made  up  of  the  smaller  cells  which 
have  been  described  above  (PL  XXII.  fig.  VI.  5,  6, 
7).  In  the  biliary  ducts  which  possess  a  diameter 
beyond  sVth  of  a  line,  according  to  Kolliker,  their 
pavement  epithelium  is  replaced  by  a  cylindrical  epi- 
thelium. Finally,  the  hepatic  ducts  proper,  together 
with  the  cystic  duct  and  the  ductu-s  communis  chole- 
doclius  have  muscular  fibres  in  their  walls,  and  also  a 
considerable  number  of  minute  racemose  glands.  The 
hepatic  artery  accompanies  the  hepatic  ducts  to  the 
lobules,  supplies  them  with  very  numerous  branches, 
and  finally  terminates  in  the  capillary  plexus  of  the 
portal  vein.  This  second  apparatus,  composed  of  the 
biliary  ducts  and  the  hepatic  artery,  constitutes  a 
tubular  gland.  The  liver  then  is  made  up  of  two 
glands,  which  are  intimately  intermingled  with  each 
other ;  one  of  these  (a  blood-gland)  is  concerned  in 


GLANDS.  133 

the  secretion  of  sugar,  and  the  other  (a  tubular  gland) 
in  the  secretion  of  bile.  The  physiology  of  the  liver, 
so  well  established  by  M.  Claude  Bernard,  as  well  as 
its  comparative  anatomy,  entirely  justify  this  view. 

The  mode  of  origin  of  the  radicles  of  the  hepatic 
duct  has  been  the  object  of  varied  researches,,  and  the 
number  of  theories  which  have  been  proposed  in 
explanation  of  it  are  evidence  of  the  uncertainty 
which  surrounds  the  subject.  We  have  admitted 
that  the  liver  is  made  up  of  two  distinct  glands, 
because,  as  we  have  already  said,  both  physiology  and 
comparative  anatomy  unite  to  prove  it,  and  we  have 
described  the  radicles  of  the  hepatic  ducts  as  tubes 
terminating  in  blind  extremities,  because  we  have 
witnessed  this  fact  twice  in  a  cirrhotic  liver,  and  we 
know  that  Professor  Kiiss*  had  already  observed  the 
same  several  years  since  in  a  syphilitic  liver.f 

*  Professor  of  Pathological  Anatomy  in  the  Faculty  of  Strasbourg, 
France.—^.) 

t  It  will  be  observed  that  our  author,  in  his  very  succinct  account  of 
the  minute  anatomy  of  the  liver,  makes  no  allusion  to  the  labors  of  Kier- 
nan,  Lereboullet,  or  Beale,  an  omission  which  cannot  be  fairly  over- 
looked. These  authors  throw  too  much  light  upon  the  mueh-debated 
question  of  the  mode  of  origin  of  the  radicles  of  the  hepatic  duct  to  be 
passed  over  in  silence.  The  best  supported  opinion  on  this  subject  at  the 
present  day  is  not  that  the  radicles  of  the  hepatic  ducts  are  merely  tubes 
terminating  in  blind  extremities,  as  stated  in  the  text,  but  that  these 
radicles  take  their  origin  from  a  Mliary  plexus  or  network  of  tubes,  ana- 
logous to  the  network  of  blood-vessels  in  the  interior  of  the  hepatic 
lobule,  and  occupying  its  interstices.  Kiernan  first  described  and  figured 
this  "  biliary  plexus"  in  his  admirable  paper  on  u  the  Anatomy  and  Phy- 
siology of  the  Liver,"  in  the  Philosophical  Transactions,  London,  1843, 
(part  1st,  p.  741,  and  PI.  XXIII.  fig.  III).  His  figure,  however,  is  dia- 
grammatic, and  not  taken  from  nature.  It  has  been  reproduced  in  most 
of  the  works  on  Descriptive  Anatomy  of  the  present  day. 

I*  1853,  M.  Lereboullet  published  a  prize  essay,  in  Paris,  u  on  the  Mi- 


134  GLANDS. 

The  walls  of  the  gall-bladder  are  composed  of  the 
same  elements  as  those  of  the  larger  biliary  ducts. 
Its  mucous  membrane  has  numerous  folds  and  rugse 

nute  Structure  of  the  Liver"  in  which,  after  very  thorough  investigation 
of  the  subject,  he  arrives  at  the  conclusion  that  Kiernan's  hypothesis  is 
correct,  and  that  the  biliary  plexus  is  truly  demonstrable,  although,  after 
long  and  laborious  research,  he  was  not  able  to  demonstrate  the  existence 
of  the  membrane  forming  the  Avails  of  the  tubes  composing  it.  He 
speaks,  however,  with  confidence,  of  the  network  of  tubes,  or  biliary 
plexus,  containing  the  secreting  cells  of  the  liver  (hepatic  cells),  as  occu- 
pying the  interstices  of  the  vascular  plexus  of  the  lobule — so  that  the  two 
sets  of  tubes,  biliary  and  vascular,  interlace  with  each  other  accurately, 
the  walls  of  the  bile-tubes  being  everywhere  so  closely  adherent  to  the 
external  surfaces  of  the  blood  capillaries  that  the  former  were  riot  sus- 
ceptible of  separate  demonstration  (p.  59  et  seq.). 

In  a  Monograph  by  Dr.  Lionel  S.  Beale  (on  some  points  in  the  Ana- 
tomy of  the  Liver  of  Man  and  Vertebrate  Animals,  London,  1856),  the 
following  passage  occurs  in  the  summary  of  his  able  and  interesting 
investigations  on  this  subject : 

"  The  liver  cells  lie  within  a  tubular  network  of  basement  membrane, 
which  separates  them  from  the  walls  of  the  capillaries.  In  many  cases, 
however,  these  thin  membranous  tubes  cannot  be  separated,  and  are,  no 
doubt,  incorporated  with  each  other." 

"  The  cell-containing  network  is  directly  continuous  with  the  most 
minute  ducts,  which  ramify  at  the  circumference  of  the  lobule,  and  it 
.  terminates  in  the  centre  by  loops,  which  lie  close  to  the  intralobular 
vein.'1  (p.  74.) 

Both  Lereboullet  and  Beale  describe  the  tubes  composing  the  "  cell- 
containing  network"  as  larger  in  diameter  than  the  "  minute  ducts," 
which  are  the  radicles  of  the  hepatic  duct.  "  The  tubes  of  the  cell-con- 
taining network  are  about  ToV^tn  of  an  inch  in  diameter,  or  more,  but 
the  finest  ducts  are  commonly  not  more  that  3  oVotn?  an<^  tnev  are  °ften 
seen  even  less."  .  .  .  "The  smallest  ducts  are  lined  with  a  very  delicate 
layer  of  epithelium,  composed  of  flattened  cells  of  a  circular  form,  con- 
trasting remarkably  with  the  large  secreting  cells" — the  hepatic  cells 
proper,  which  occupy  the  cell- containing  network,  or  biliary  plexus. 
(Beale,  p.  74.) 

In  addition  to  the  evidence  we  have  quoted,  which  sets  forth  what  we 
believe  to  be  the  true  anatomy  of  the  liver  in  relation  to  the  point  in 
question,  the  monographs  of  Lereboullet  and  Beale  may  be  advanta- 


GLANDS.  135 

upon  its  surface,  the  intersection  of  which  gives  it  a 
honey-combed  appearance  ;  it  is  lined  by  a  cylindrical 
epithelium,  composed  of  yellowish  colored  cells,  which 
are  very  pale  and  often  destitute  of  nuclei  (PL  XXII. 
fig.  V.). 

The  liver  has  two  sets  of  lymphatics  :  one  super-  Lymphatics. 
ficial,  ramifying  in  the  thickness  of  its  proper  coat  ; 
the  other  deep,  and  following  the  subdivisions  of  the 
portal  vein  ;  they  anastomose  freely  with  each  other, 
and  terminate,  those  from  the  convex  surface  of  the 
organ,  by  passing  upwards  through  the  thoracic 
cavity,  and  those  from  its  inferior  surface,  by  running 
into  the  lymphatic  glands  of  the  abdomen. 

The  nerves  of  the  liver,  which  are  derived  from  the 
pne  in  no-gas  trie  and  great  sympathetic,  join  the  hepa- 
tic artery  and  follow  its  ramifications  ;  but  their  mode 
of  termination  in  the  interior  of  the  lobules  is  un- 
known. 

The  first  traces  of  the  liver  make  their  appearance  Development. 
in  the  shape  of  two  little  masses  of  cells,  one  upon 
the  outer,  the  other  upon  the  inner  or  epithelial  layer 
of  the  intestinal  wall.  As  to  their  subsequent  meta- 
morphoses, what  has  been  ascertained  by  the  most 
reliable  einbryologists  may  be  stated  as  follows: 
Whilst  the  more  external  of  the  two  cellular  masses 
enlarges  and  surrounds  the  common  trunk  formed  by 
the  umbilical  and  portal  veins,  constituting  thus  a 
parenchymatous  mass  enclosing  the  portal  system  of 
veins  which  are  closely  enveloped  by  large  sized 

geously  consulted  by  the  student  ;  they  contain  much  valuable  informa- 
tion as  to  injecting  and  preparing  specimens  of  the  liver  for  micro- 
scopical study.—  (Ed) 


136  GLANDS. 

hepatic  cells,  the  internal  mass  sprouts  into  numerous 
tubular  branches  which,  penetrating  the  substance  of 
the  outer  mass,  constitute  the  system  of  biliary 
ducts.  Whilst  these  changes  are  taking  place,  the 
original  primordial  cells,  of  which  the  masses  were 
composed,  undergo  various  metamorphoses  which 
result  in  the  formation  of  the  several  tissues  consti- 
tuting the  substance  of  the  gland. 

preparations.  The  preparations  on  which  the  structure  of  the 

liver  is  best  studied  are  very  delicate  sections  of  the 
fresh  liver,  and  also  of  livers  injected  with  colors 
ground  in  oil  and  diluted- with  essence  of  turpentine. 

3Utfeeinteft?ned88          SECT.  IV.    DUCTLESS  FOLLICLES  AND  BLOOD  GLANDS. 

— The  most  simple  in  their  structure  of  this  class  of 
organs  are  the  solitary  glands  of  the  intestinal  canal. 
These  are  little  spherical  bodies,  situated  deeply  in 
its  mucous  membrane,  and  varying  from  half  a  line 
•to  one  line  in  diameter.  Their  walls  consist  of  fibroid 
membrane  studded  thickly  with  plasmatic  ceils.  Their 
contents,  greyish  in  color,  and  of  a  solid  consistence, 
are  made  up  of  a  quantity  of  rounded  globules,  from 
aFifth  to  T^jth  of  a  line  in  diameter,  and  bearing  a 
very  close  resemblance  to  the  cells  contained  in  the 
interior  of  the  lymphatic  glands.  Numerous  blood- 
vessels ramify  upon  their  exterior,  and  then,  penetrat- 
ing their  walls,  converge  towards  the  centre  of  each 
follicle.  Externally  to  the  follicle  they  anastomose 
freely,  but  towards  its  centre  they  form  a  great  number 
of  loops,  which,  when  filled  by  injection,  present  a  very 
beautiful  appearance  (PL  XXVI.  fig.  XIII.  2).  Kol- 
liker  has  found  nerves  in  the  follicles  of  the  tongue, 
,  according  to  this  author,  E.  Weber  has  also 


GLANDS. 

recognised  in  them  radicles  of  lymphatics.  No  exter- 
nal outlet  has  been  discovered,  after  the  most  rigor- 
ous examination  of  the  external  surfaces  of  these 
glands.  Reasoning  from  the  structure  of  these 
organs,  and  also  from  certain  pathological  relations 
existing  between  them  and  the  mesenteric  glands,  the 
conclusion  seems  to  us  legitimate  that  they  are  iden- 
tical in  their  nature  with  lymphatic  glands.  This 
opinion  is  sustained,  also,  by  the  most  distinguished 
histologists  of  Germany.  These  ductless  glands  are 
what  are  known  as  the  solitary  glands  of  the  intes- 
tine ;  they  constitute  the  essential  portion  of  Peyer's 
glands,  of  the  tonsils,  the  follicles  of  the  tongue,  and 
the  pharynx.  The  structure  of  the  vesicles  of  the 
thymus  gland  warrants  us  also  in  including  it  in  the 
same  category. 

Thyroid  body. — The  fibrous  envelop  of  the  thyroid  Thyroid  body 
body  gives  off  from  its  internal  surface  a  great  num- 
ber of  delicate  trabeculse  of  connecting  tissue  by  which 
its  interior  is  divided  up  into  spaces,  or  cavities,  in 
which  the  vesicles,  of  the  gland  are  contained  (PL 
XXII.  fig.  VIII.) .  Each  vesicle  is  thus  enclosed  by 
a  delicate  partition  of  connective  fibres,  in  the  sub- 
stance of  which  a  considerable  number  of  plasmatic 
cells  are  found,  together  with  an  abundance  of  ves- 
sels (fig.  VIII.  2,  3).  A  single  layer  of  polygonal 
epithelium  lines  the  interior  of  the  vesicle,  and  its 
cavity  is  filled  with  an  albuminous  fluid.  In  the 
foetus,  and  young  child,  the  epithelial  layer  consists 
of  cells  Troth  of  a  line  in  diameter,  with  finely  granu- 
lar contents,  and  a  nucleus  measuring  about  zieth  of 
a  line.  But  in  the  adult,  and  in  old  age,  it  is  very 

9 


138  GLANDS. 

difficult  to  find  the  epithelium  well  marked  and  dis- 
tinctly separate  from  the  liquid  contents  of  the  vesi- 
cle; most  frequently  its  cells  are  found  infiltrated 
with  fat,  and  a  large  number  of  free  oil  globules  and 
nuclei  are  contained  in  the  liquid  which  fills  the  vesi- 
cle, which  is  evidence  of  the  disintegration  and  break- 
ing down  of  its  elements  (fig.  VIII.  4).  It  is  doubtless 
in  these  vesicles,  or  follicles,  of  the  thyroid,  that  most 
of  the  morbid  growths  to  which  the  gland  is  liable, 
take  their  origin.  The  lobulated  shape  of  the  thyroid 
body  depends  upon  the  aggregation  of  its  follicles 
into  little  masses,  or  lobules,  which  remain  to  a  cer- 
tain extent  independent  of  each  other. 
vessels.  The  blood-vessels  of  the  thyroid  are  remarkable 
for  their  size  and  number,  and  the  rich  and  delicate 
plexuses  of  capillaries  which  they  form  around  the 
walls  of  each  follicle.  Its  nerves  come  from  the 
sympathetic ;  with  regard  to  their  mode  of  termina- 
tion, as  well  as  to  the  distribution  of  its  lymphatics, 
nothing  is  certainly  known. 

Development.  The  facts  ascertained  thus  far  in  relation  to  the 
development  of  the  thyroid  gland  are  not  sufficiently 
accurate  and  positive  to  justify  their  record  in  this 
work. 

spleen.  Spleen. — The  spleen  is  an  organ  in  regard  to  the 
structure  of  which  much  remains  yet  to  be  elucidated ; 
the  following  account  includes  all  that  the  labors  of 
the  most  eminent  microscopic  anatomists  have  thus 
far  established  as  certain. 

The  envelop  of  this  vascular  gland  is  similar  to 
that  of  the  liver,  and  is  intimately  adherent,  exter- 
nally, to  the  peritonaeum,  and  internally,  to  its  paren- 


GLANDS.  139 

ch  yma ;  at  the  hilus  of  the  organ  it  is  reflected  upon 
its  vessels,  and  accompanying  them  into  its  interior, 
forms  a  sort  of  capsule  of  Glisson. 

Its  parenchyma  consists  of  a  sort  of  coi^pus  caver-  p*«mchyma. 
no-sum,  the  trabeculse  of  which,  fibrous  in  their  nature, 
are  continuous  by  their  extremities  with  the  inner 
surface  of  the  proper  coat  of  the  organ,  and  in  their 
interspaces  is  a  soft  material  very  closely  resembling 
blood-clot,  called  the  pulp  of  the  spleen.  There  are 
also  certain  spherical  bodies  connected  with  its  arte- 
ries, and  called  corpuscles  of  Malpighi,  which  form  a 
portion  of  the  parenchyma  of  the  organ. 

We  have  said  that  the  fibrous  coat  of  the  spleen 
was  reflected  upon  its  vessels,  and  constituted  for 
them  a  sheath  or  capsule,  continuous,  in  its  interior, 
with  the  trabeculse.  The  splenic  artery  gives  off 
near  its  hilus,  a  certain  number  of  branches,  which, 
as  they  penetrate  the  substance  of  the  gland,  con- 
tinue independent  of  each  other,  and  form,  each  one 
of  them,  by  its  subdivisions,  a  sort  of  vascular  brush. 
Situated  upon  arterioles  of  from  eVth  to  *Vth  of  a  line 
in  diameter  are  the  little  rounded  whitish  colored 
bodies  already  mentioned  as  the  corpuscles  of  Mal- 
pighi ;  they  measure  from  one-eighth  to  one-fourth 
of  a  line  in  diameter.  Their  structure  is  identical 
with  that  of  the  solitary  glands  of  the  intestinal 
canal.  They  have  a  very  delicate  outer  coat  of  con- 
necting tissue,  which  is  continuous  with  the  sheath  of 
the  artery  upon  which  each  corpuscle  is  situated,  and 
its  contents  are  made  up  of  the  same  elements  that  we 
find  in  the  interior  of  a  lymphatic  gland,  viz.,  spheri- 
cal cells  of  from  3 loth  to  rioth  of  a  line  in  diameter, 


140  GLANDS. 

and  free  nuclei ;  Kolliker  mentions  also  the  presence 
of  blood  globules,  both  normal  in  appearance,  and 
in  various  stages  of  alteration.  Leydig  has  described 
a  vascular  network  which  penetrates  the  interior  of 
the  corpuscle,  and  thus  completes  its  resemblance  to 
a  ductless  gland  ;  this  author,  in  fact,  does  not  hesitate 
to  consider  the  Malpighian  corpuscle  of  the  spleen  as 
a  minute  lymphatic  gland. 

spiemc  puip.  The  splenic  pulp,  the  substance  of  which  is  tra- 
versed by  the  finest  vessels,  and  the  most  delicate 
trabeculse,  includes  elements  of  different  kinds.  Its 
principal  bulk  consists  of  cells  similar  to  those  of  the 
Malpighian  corpuscles  (PI.  XXII.  fig.  VII.  1)  ;  debris 
of  red  blood  globules,  blood  pigment,  and  larger 
cells  with  many  nuclei,  joth  of  a  line  in  diameter, 
make  up  the  remainder.  In  some  of  these  latter 
elements  the  formation  of  red  globules  seems  to  take 
place  by  endogenous  vegetation ;  at  least  this  is  to  be 
inferred  from  the  drawing  by  Otto  Funke,*  in  his 
Atlas  of  Physiological  Chemistry.  But  Kolliker 
asserts,  on  the  contrary,  that  these  cells  are  at  first 
nothing  more  than  aggregations  of  red  globules, 
around  which  a  membrane  has  formed,  thus  consti- 
tuting a  cell,  of  which  these  old  blood  globules 
become  the  nuclei,  and  that  they  are  about  to  undergo 
still  farther  metamorphoses  in  a  retrograde  direction, 
of  which  he  gives  drawings  confirmatory  of  his 
opinion.  Are  we  to  conclude  then,  with  Otto  Funke, 
that  red  globules  of  the  blood  are  formed  in  the 

*  Formerly  Professor  of  Physiology  in  the  University  of  Leipzig ;  at 
present  occupies  the  same  chair  at  Freiburg,  Grand  Duchy  of  Baden, 
Germany. — (Ed.) 


GLANDS.  141 

spleen,  or,  with  Kolliker,  that  it  is  an  organ  whose 
function  is  to  destroy  them  ? 

Amongst  the  elements  of  the  spleen  there  remain 
to  be  noticed  some  cells  of  a  fusiform  shape,  very 
much  enlarged  around  their  nuclei  (fig.  VII.  2).  In 
comparing  these  corpuscles  with  the  epithelial  cells 
of  the  vessels,  it  is  difficult,  from  their  similarity  of 
shape,  not  to  regard  them  as  identical  in  nature 
Nevertheless,  Fiihrer*  (Gazette  hebd.,  1855,  p.  314), 
takes  a  different  view  of  them,  and  assigns  to  them 
an  important  physiological  function.  According  to 
his  view,  these  fusiform  cells,  swelled  out  like  so 
many  aneurisms,  are  nothing  more  than  tubes  con- 
nected to  each  other,  end  to  end,  and  communicating 
with  the  capillaries  of  the  spleen,  whilst  their  nuclei 
are  the  future  red  blood  globules.  Fiihrer  has  doubt- 
less allowed  himself  to  be  carried  away  by  the  desire 
to  establish  an  analogy  between  these  fusiform  bodies 
and  the  arterial  dilatations  which  exist  in  fishes,  and 
he  has  overlooked  their  epithelial  character. 

The  smallest  of  the  veins  spring  from  the  capil-  veins,  etc. 
laries,  run  alone  for  a  short  distance,  and  then  join 
the  arteries.  The  lymphatics,  superficial  and  deep, 
meet  and  unite  at  the  hilus,  whence  they  are  trans- 
mitted directly  to  the  thoracic  duct.  The  nerves  of 
the  spleen  are  numerous ;  they  are  distributed  with 
its  arterial  branches,  and  seem  to  terminate  by  free 
extremities. 

It  is  a  matter  of  extreme  difficulty  to  determine 
the  relations  which  exist  between  the  splenic  pulp, 

*•  A  practising  physician  at  Hamburgh,  author  of  a  popular  work  on 
Surgical  Anatomy. — (Ed.) 


142  GLANDS. 

and  the  larger  veins  of  the  organ.  Is  the  pulp 
entirely  outside  of  the  vessels,  as  asserted  by  some 
authorities,  or  are  the  spaces  in  which  it  is  contained 
simply  dilatations  of  the  veins,  and  if  this  be  true, 
does  it  form  a  part  of  the  general  circulation  ?  The 
researches  which  seem  to  us  most  conclusive  tend 
rather  to  establish  the  entire  independence  of  the 
cavities  which  contain  the  splenic  pulp ;  yet  the  fact 
is  not  to  be  accepted  as  demonstrated. 

Development  It  is  not  agreed  at  what  point  exactly  the  spleen 
takes  Us  origin,  Arnold  asserts  that  at  first  (from 
the  seventh  to  the  eighth  week),  it  is  confounded 
with  the  pancreas.  BischofP  says  that,  in  the  fcetal 
calf,  he  has  seen  it  spring  from  the  greater  curvature 
of  the  stomach ;  and  according  to  other  observers,  it 
is  developed  from  a  blastema,  at  first  isolated,  but 
which  shortly  becomes  attached  to  the  great  cul-de- 
sac  of  the  stomach.  As  to  the  histological  transfor- 
mations which  the  organ  undergoes  during  its  increase 
of  size>  they  have  not  been  accurately  demonstrated. 
*H>"  Supra-renal  Capsules. — The  nature  and  physio- 
logical function  of  these  organs  are  as  yet  unknown. 
Nevertheless  it  seems  probable,  from  the  nature  of 
certain  elements  which  enter  into  their  composition, 
and  which  form,  in  fact,  almost  the  whole  of  their 
central  portion,  that  they  belong  rather  to  the  ner- 
vous system  than  to  the  class  of  glands  under  consi- 
deration. 

structure.       The  supra-renal  capsule  possesses  a  thin  envelop, 
fibrous  in  its  structure,  and  intimately  connected  with 

*  Professor  of  Physiology  at  Heidelberg,  Baden,  Germany. — (Ed.) 


GLANDS.  143 

the  parenchyma  of  the  organ  by  delicate  processes,  or 
trabeculse,  given  off  from  its  internal  surface. 

On  making  a  section  completely  through  the  body  £°8rtical  8Ubfitafl' 
of  the  organ  it  is  found  to  consist  of  two  distinct  sub- 
stances, of  which  one  forms  its  cortical  portion,  and 
the  other  its  centre.  The  first,  or  cortical  substance, 
one-half  a  line  to  a  line  in  thickness,  is  of  a  soft,  solid 
consistence  and  brownish  color,  being  of  a  somewhat 
deeper  tint  externally  than  internally.  In  the  fibril- 
lated  tissue  which  forms  its  basis  are  a  number  of 
elongated  cavities  filled  with  large  cells  (from  y£oth 
to  irVth  of  a  line  in  diameter)  and  very  much  infil- 
trated with  fat. 

The  fibrillated  element  of  its  central  or  medullary 
substance  is  more  delicate  than  that  of  its  outer  por- 
tion, and  the  cells  which  it  contains  resemble  exactly 
the  multipolar  or  caudate  cells  of  the  nervous  gan- 
glia. The  numerous  nerves  with  which  the  supra- 
renal capsule  is  supplied  penetrate  this  substance,  and 
unite,  as  Leydig  has  demonstrated,  with  the  prolon- 
gations of  these  nerve  cells.  We  haye'a  right,  then, 
in  accordance  with  these  facts,  to  regard  this  organ 
as  a  nervous  centre,  and  to  consider  its  cortical  layer 
as  simply  a  protecting  membrane,  for  the  very  con- 
siderable amount  of  fatty  infiltration  of  its  cellular 
element  seems  to  indicate  an  arrest  of  its  functional 
activity.* 

*  In  one  of  the  most  aggravated  instances  of  hysterical  temperament 
that  I  have  ever  encountered,  the  patient,  a  maiden  lady,  died,  at  the  age 
of  84,  of  cancer.  The  cancerous  deposit  involved  both  supra-renal  cap- 
sules, which  were  each  as  large  as  the  closed  fist;  the  right,  which  was 
somewhat  the  larger,  having  imbedded  itself  firmly  in  the  under  surface 
of  the  liver.  There  was  also  a  cancerous  mass  in  the  posterior  wall  of 


144  GLANDS. 

vessels.  Its  arteries  and  veins  are  numerous ;  in  their  mode 
of  distribution  they  present  no  peculiarities  worthy 
of  note.  The  lymphatics  are  few  in  number,  and 
seem  to  belong  to  the  cortical  substance  alone.  The 
development  of  the  supra-renal  capsule  takes  place  at 
the  same  time  with  that  of  the  kidney,  but  entirely 
independently  of  that  organ.  Of  the  histological 
transformations  which  it  undergoes  during  foetal  life 
little  is  known. 

the  transverse  colon,  and  another  in  the  root  of  the  right  lung.  This 
latter,  by  its  pressure  upon  the  pulmonary  veins,  the  interior  of  which  it 
had  also  invaded,  gave  rise  first  to  haemoptysis,  and  afterwards  to  exten- 
sive pleuritic  effusion— from  the  immediate  effects  of  which  death  took 
place.  The  most  prominent  abnormal  nervous  phenomenon  manifested 
by  this  patient,  which  continued  during  her  whole  life,  and  included  most 
of  her  multifarious  ailments,  was  excessive  general  hyper-sesthesia  with 
great  mobility  of  the  nervous  system.— (Ed.) 


CHAPTER   VIII. 
Skin  and  its  Appendages. 

SECT.  I.  SKIN. — The  skin  consists  of  two  distinct  Epidermis, 
layers :  the  first,  superficial,  and  composed  entirely  of 
cells,  is  the  epidermis,  or  cuticle ;  the  second,  beneath 
this,  which  has  for  its  basis  a  dense  interlacement  of 
fibres  of  connecting  tissue,  containing  in  its  meshes  a 
quantity  of  nerves,  blood-vessels,  glands,  and  masses 
of  adipose  cells,  is  the  derma,  or  true  skin. 

In  the  epidermis  there  are  three  distinct  strata. 
The  first,  in  contact  with  the  true  skin,  consists  of  a 
single  layer  of  cylindrical  cells  with  well  marked 
nuclei,  and  with  their  long  diameters  at  right  angles 
to  its  surface  (PL  XXIII.  fig.  II.  3  ;  fig.  III.  1 ;  fig.  IV. 
3).  It  is  principally  in  this  layer  that  the  deposit  of 
black  pigment  is  found  which  causes  the  dark  color 
of  the  negro,  and  in  certain  regions  of  the  skin  in  the 
white,  as,  for  example,  the  nipple  and  the  scrotum 
(fig.  III.  1),  Upon  this  stratum  of  cylindrical  cells 
is  another,  five  or  six  times  the  thickness  of  the  first, 
and  likewise  consisting  of  nucleated  cells  (fig.  I.  3  ; 
fig.  II.  2).  The  deepest  cells  of  this  layer  are  oval, 
the  next  in  order,  round,  or  regularly  polygonal,  and 
the  most  superficial  again  oval ;  but  their  long  dia- 
meters have  a  different  direction  from  those  of  the 
deep  cells ;  that  is,  they  are  parallel  to  the  cutaneous 
surface.  It  is  these  two  united  layers  which  form  the 


146  SKIN   AND   ITS    APPENDAGES. 

rete  mucosum  of  Malpighi.  Finally,  the  third  stratum 
or  horny  layer,  very  variable  in  its  thickness,  is  com- 
posed entirely  of  scale-like  cells,  which  overlie  each 
other  regularly  (fig.  I.  2;  fig.  II.  1),  and  which  differ 
from  the  cells  of  the  rete  mucosum,  not  only  in  their 
form,  but  also  in  the  absence  of  their  nuclei,  and  in 
their  contents,  which  are  more  or  less  opaque,  and 
coarsely  granular.  They  resist  also  for  -a  longer  time 
the  action  of  acetic  acid,  and  caustic  potash. 

The  epidermis,  like  the  other  epithelial  membranes, 
has  neither  vessels  nor  nerves,  but  it  does  not,  on  this 
account,  possess  in  any  less  degree  true  organization 
and  indubitable  vitality. 

Derma.  The  true  skin  is  naturally  divisible  into  two  strata, 
which  insensibly  mingle  with  each  other  along  their 
line  of  contact.  The  deep,  or  reticulated  layer  is 
made  up  of  a  loose  interlacement  of  connective  and 
elastic  fibres  which,  on  its  internal  surface,  become 
continuous  with  those  which  go  to  form  the  super- 
ficial fascia.  It  is  in  this  reticulated  stratum  of  the 
derma  that  we  find  its  glands,  the  hair  follicles,  and 
fat  cells,  grouped  together  in  little  rounded  masses. 
(PL  XXIII.  fig.  I.  8,  10.)  It  is  here  also  that  its 
blood-vessels  ramify  and  give  off  their  ultimate 
branches,  which  are  distributed  to  the  superficial 
layer. 

The  surface  of  the  superficial  or  papillary  layer  of 
the  true  skin  is  studded  with  minute  projections 
known  as  its  papillae.  These  papillae  are  not  every- 
where uniformly  distributed,  nor  do  they  present 
everywhere  the  same  volume ;  they  are  most  numerous 
and  largely  developed  on  the  extremities  of  the  fin- 


SKIN   AND   ITS   APPENDAGES. 

gers  and  toes,  and  upon  the  palms  of  the  hands  and 
soles  of  the  feet ;  some  of  them,  in  these  localities,  are 
even  surmounted  by  secondary  papillae. 

The  papillae,  as  well  as  the  portion  of  the  derma 
from  which  they  project,  are  composed  of  very  deli- 
cate fibrous  tissue,  containing  a  large  number  of  plas- 
matic  cells  (fig.  II.  5),  and  tunnelled  by  the  terminal 
branches  of  the  vascular  and  nervous  systems.  The 
papillary  surface  of  the  true  skin  is  limited  by  a  very 
delicate  structureless  membrane  (reVoth  of  a  line  in 
thickness),  which  separates  it  from  the  epidermis 
(fig.  II.  4). 

The  blood-vessels  of  the  skin  form  two  sets :  one  vessels. 
occupies  the  deep  stratum,  and  supplies  the  glands, 
hair  follicles,  and  pellets  of  fat;  the  other,  in  the 
shape  of  a  close  network,  is  found  spread  out  in  the 
superficial  layer,  where  it  gives  off  the  terminal 
loops  which  penetrate  the  interior  of  most  of  the 
papillae. 

The  nervous  filaments  of  the  deep  layer,  few  in  -servef. 
number,  are  destined  for  the  supply  of  the  organs 
which  it  contains,  whilst  those  of  the  papillary  layer  are 
very  numerous,  forming  a  plexiform  network  which 
seems  to  terminate,  after  previous  sub-divisions,  by 
free  extremities.  A  large  number  of  these  ultimate 
nervous  filaments  enter  the  bases  of  a  certain  propor- 
tion of  the  papillae  (nervous  papillae),  and  terminate 
there  either  by  free  extremities,  more  rarely  by  form- 
ing loops,  or  lastly  by  olive-shaped  extremities,  which 
constitute  the  tactile  corpuscles  already  described 
(PL  XXIII.  fig.  II.  6).  It  will  be  recollected,  also, 
that  the  Paccinian  corpuscles  constitute  another  mode 


148  SKIN   AND   ITS   APPENDAGES. 

of  termination  of  the  cutaneous   nerves  (PL  XIV 

%.  ii). 

lymphatics.  The  lymphatics  of  the  skin  form  a  very  close  web  in 
the  papillary  layer,  communicating  by  larger  branches 
with  the  subcutaneous  vessels  of  the  same  system. 
We  possess  no  positive  information  as  to  their  mode 
of  origin.  M.  Kiiss  asserts  that  they  are  in  direct 
communication  with  the  deep  stratum  of  the  epi- 
dermis. 

The  cutaneous  glands  have  been  already  described. 
Development.  According  to  Bischoff,  the  skin  can  be  distinguished 
as  a  distinct  membrane  as  early  as  the  commence- 
ment of  the  second  month  of  foetal  life.  The  true 
skin,  as  yet  consisting  entirely  of  embryonic  cells, 
very  soon  acquires  an  increased  degree  of  density, 
and  becomes  distinct  from  the  epidermis  ;  later,  the 
cells  are  metamorphosed,  some  of  them  into  connec- 
tive and  elastic  fibres,  and  others  into  vessels,  etc. 
Finally,  a  certain  proportion  of  them  seem  to  undergo 
a  temporary  arrest  in  their  development,  and  consti- 
tute what  have  been  denominated  plasrnatic  cells. 
As  for  the  epidermis,  it  is  developed  by  the  multi- 
plication and  increase  in  volume  of  its  globular  ele- 
ments. Although  the  fact  has  not  as  yet  been 
demonstrated,  it  is  probable  that  this  multiplication 
of  cells  is  effected,  both  in  the  embryo,  and  through- 
out life,  by  the  endogenous  generation  of  new  nuclei, 
and  subsequent  cleavage  of  the  parent  cell. 

Preparation.  To  study  its  structure,  very  thin  sections  both  of 
recent  and  dried  skin,  must  be  made  by  a  razor. 
Acetic  acid  renders  these  sections  more  transparent, 
and  caustic  potash  has  the  same  effect,  but  breaks 


SKIN    AND   ITS    APPENDAGES.  149 

down  their  tissue ;  these  reagents,  therefore,  are  useful 
in  bringing  out  their  details  of  structure.  Tactile 
corpuscles  are  best  found  in  sections  of  the  skin  of  the 
palmar  surface  of  the  third  phalanges  of  the  fingers, 
and  in  the  corresponding  portions  of  the  toes. 

SECT.  II.  NAILS. — The  substance  of  the  nails  is 
nothing  more  than  a  peculiar  form  of  hypertrophy 
of  the  epidermis.  The  deep  surface  of  this  horny 
plate  rests  directly  upon  the  true  skin ;  its  anterior 
margin  is  free,  whilst  its  posterior  and  lateral  borders 
are  received  into  a  groove  formed  by  a  fold  of  the 
true  skin  (PL  XXIV.  fig.  I.  II.  IIL).  ' 

On  the  surface  of  the  derma,  in  contact  with  the  Matrix. 
deep  surface  of  the  nail,  known  as  its  matrix,  we 
find  numerous  delicate  ridges  which  run  parallel  with 
each  other  and  with  the  axis  of  the  limb,  converging 
at  the  root  of  the  nail  towards  a  common  centre,  and 
usually  possessing  no  papillae.  With  these  exceptions 
the  structure  of  the  matrix  of  the  nail  is  the  same  as 
that  of  the  true  skin  elsewhere  ;  its  two  strata  exist 
as  usual ;  it  is  to  be  noticed,  however,  that  its  vascu- 
lar network  is  less  rich  towards  the  root  of  the  nail, 
causing  a  dead  white  surface  of  the  semilunar  shape 
(the  lumda)  partly  covered  by  the  margin  of  the 
fold  of  the  skin,  into  which  the  posterior  border  of 
the  nail  is  received. 

It  consists  of  both  of  the  layers  of  which  the  skin 
is  formed,  but  the  dermal  layer  is  destitute  of  papil- 
Ise  (fig.  I.  5). 

In  the  nail  we  find  a  repetition  of  the  three  strata  structure  of 
of  cells  which  we  have  seen  forming  the  epidermis. 
The  middle  and  deep  layers  are  identical  with  those 


150  SKIN   AND    ITS   APPENDAGES. 

of  the  epidermis,  and  continuous  with  them  without 
any  line  of  demarcation  (fig.  II.  2,  7).  In  the 
superficial  stratum,  the  distinctive  characteristics  in 
which  it  differs  from  the  corresponding  layer  of  the 
cuticle  are :  the  persistence  of  the  nuclei  of  its  cells, 
the  greater  transparency  of  their  contents,  and  a 
firmer  cohesion  of  the  cells  to  each  other. 

The  epidermis  of  the  fold  at  the  root  of  the  nail 
adheres  closely  to  its  surface  (fig.  II.  10),  but  as  its 
component  cells  are  not  exactly  identical  with  those 
of  the  surface  of  the  nail,  there  results  a  very  distinct 
line  of  demarcation  between  the  two  otherwise  con- 
tinuous layers  (fig.  II.  4). 

Development.  As  early  as  the  third  month,  the  groove  which 
receives  the  root  and  sides  of  the  nail  is  apparent. 
Both  the  true  skin  and  epiderm  become  slightly 
hypertrophied,  and  by  the  fifth  month,  the  laminated 
ridges  of  the  derma  have  become  visible,  and" the  nail 
is  distinguishable  from  the  surrounding  cuticle — with 
which  it. is  continuous. 

Growth.  The  growth  of  the  nail  takes  place  at  the  expense 
of  the  rete  mucosum,  the  more  superficial  cells  of 
which  become  successively  transformed  into  scales  of 
horn.  Its  increase  in  length  is  effected  by  the  active 
vegetation  of  the  cells  at  the  bottom  of  the  groove 
which  lodges  its  root,  they  becoming  continuous  with 
its  substance.  Whilst  it  is  thus  pushed  forwards,  the 
deep  surface  of  the  nail  appropriates  a  portion  of  the 
cells  generated  from  the  surface  of  its  matrix,  and  it 
thus  grows  in  thickness  ;  but  the  growth  in  length  is 
by  far  the  more  rapid  of  the  two  processes. 

In  the  study  of  its  structure,  similar  preparations 


SKIN    AND    ITS   APPETOAGES.  151 

are  required  to  those  of  the  skin ;  the  use  of  dilute 
solution  of  potassa  is  required  to  separate  the  cells 
of  the  horny  lamina. 

SECT.  III.  HAIR, — The  hairs,  like  the  nails,  are  Hair, 
composed  of  epithelium.  A  hair  is  a  delicate  cylin- 
der, generally  more  or  less  flattened,  variable  in  its 
dimensions,  and  consisting  of  two  distinct  portions: 
the  shaft,  which  projects  beyond  the  surface  of  the 
skin,  and  the  root  which'is  imbedded  in  a  sheath,*  or 
follicle,  furnished  by  the  skin.  This  latter  terminates 
by  a  bulbous  enlargement,  at  the  extremity  of  which 
is  a  deep  excavation,  which  is  occupied  by  one  of  the 
papillae  of  the  skin  (germ,  pulp,  papilla  of  the  hair, 
PL  XXIV.  fig.  IV.  3,  7). 

The  surface  of  the  hair  is  formed  by  a  single  layer  structure. 
of  epithelium,  called  the  epidermis  of  the  hair  (PI. 
XXIV.  fig.  VII.  1)  ;  immediately  beneath  this  is 
found  a  material  arranged  in  longitudinal  striae  which 
constitutes  almost  the  entire  bulk  of  the  hair,  and 
which  is  known  as  its  cortical  substance  (fig.  VII.  2) ; 
finally,  in  the  centre  of  the  shaft  there  is  generally, 
but  not  always,  a  canal  filled  by  cells  of  a  peculiar 
shape,  which  forms  its  medullary  substance  (fig. 
VIL  3). 

The  epidermis  is  composed  of  a  single  layer  of  scaly  Epidermis, 
cells,  presenting  an  imbricated  arrangement,  so  that 
their  superior  margins  are  free  (PL  XXIV.  fig.  V.). 
On  treating  this  layer  with  acetic  acid,  or  caustic 
potash,  its -cells  swell  out  and  become  more  trans- 
parent, so  that  it  can  be  seen  that  their  contents 
consist  of  fine  granules,  and  that  their  nuclei  have 
disappeared  (fig.  VI.).  The  epidermis  is  found  only 


152  SKIN    AND    ITS   APPENDAGES. 

upon  the  shaft  of  the  hair,  it  ceases  abruptly  at 
the  commencement  of  its  root.  Leydig  has  repre- 
sented, as  the  epidermis  of  the  root  of  the  hair,  a 
layer  of  cylindrical  cells,  which  are  arranged  perpen- 
dicularly to  its  surface,  but  their  existence  is  by  no 
means  constant. 

?tenceal  sub"  The  cortical  substance,  the  color  of  which  varies 
with  the  hair,  is  marked  by  longitudinal  striae  and 
linear  spots,  which  run  in  •  the  same  direction  (PL 
XXIV.  fig.  VII.  2).  The  elements  of  which  it  is 
composed  cohere  very  closely,  but,  by  the  aid  of 
caustic  potassa,  they  can  be  readily  separated  and 
recognised  as  long  fusiform  bodies,  homogeneous  in 
their  structure,  without  trace  of  nuclei,  and  contain- 
ing, sometimes,  pigmentary  granules.  The  dark 
linear  spots  seem  to  be  simply  cavities  filled  with  air, 
for  they  are  found  in  white,  as  well  as  in  colored 
hairs  (PI.  XXV.  fig.  I). 

In  the  root  of  the  hair  the  cortical  substance  pre- 
sents again  a  different  appearance ;  in  the  bulb  we 
find  regular  polygonal  cells  with  clearly  defined 
nuclei,  and  granular  contents  sometimes  transparent 
and  at  others  charged  with  pigment  (PL  XXV.  fig. 
II.  6).  A  little  higher  up,  these  cells,  and  their 
nuclei  also,  become  elongated,  and  the  outlines  of  the 
cells  gradually  grow  pale  and  disappear,  whilst  their 
nuclei  continue  to  elongate,  and  remain  visible.  They 
finally,  however,  become  pale  and  disappear  also,  or, 
perhaps,  they  are  converted  into  the  fusiform  bodies 
of  the  cortical  substance  after  their  cell  walls  are 
absorbed  ? 
sub-  r  me(jnnary  canai  <joeQ  not  always  exist,  and, 


SKIN    AND    ITS    APPENDAGES.  153 

when  present,  it  varies  in  shape  and  length.  Thus, 
sometimes  it  occupies  the  whole  length  of  the  hair ; 
at  others,  it  ceases  at  the  root ;  and  again,  it  fre- 
quently presents  constricted  portions,  and  even  entire 
interruptions  (PL  XXIV.  fig.  IV.  6,  fig.  VII.  3  ;  PL 
XXV.  fig.  II.  8).  The  cells  by  which  it  is  filled  con- 
stitute the  medullary  substance ;  they  contain,  usu- 
ally, a  very  pale  nucleus,  and  fatty  looking  granules ; 
according  to  Kolliker  they  contain  also  air  bubbles. 

The  hair  follicle,  or  sheath,  which  envelops  its  root, 
recalls  in  its  structure  that  of  the  skin ;  in  fact  we 
find,  on  section  of  its  walls,  two  layers  of  connecting 
tissue  similar  to  those  of  the  skin,  and  two  other 
strata  of  cells  representing  the  epidermis.  This 
structure  suggests  the  idea,  although  the  mode  of 
development  of  the  hair  proves  the  contrary,  that  the 
hair  follicle  is  formed  by  an  indentation,  or  an  invo- 
lution, of  the  skin.  The  following,  however,  is  its 
structure : 

Proceeding  from  without  inwards,  we  recognise :  structur 
1st,  a  stratum  of  very  loose*  connecting  tissue,  which 
is  continuous  with  the  deep  layer  of  the  true  skin 
(PL  XXV.  fig.  II.  1) ;  2d,  another  stratum,  very  dis- 
tinct from  the  preceding,  and  similar  in  structure  to 
the  papillary  layer  of  the  true  skin,  with  which  it  is 
also  continuous ;  internally  this  layer  is  limited  by  a 
delicate  and  structureless  basement  membrane,  as  in 
the  skin  (fig.  II.  2,  3)  ;  3d,  reposing  upon  this  deli- 
cate line  is  the  deep  epidermic  layer,  made  up  of  cells 
whose  shape  and  mode  of  stratification  resemble  those 
of  the  rete  muoosum  (fig.  II.  4,  PL  XXVII.  fig.  V.  4); 
4th,  the  internal  epidermic  layer,  which,  with  its 

10 


154  SKIN   AND   ITS    APPENDAGES, 

scale-like  cells,  destitute  of  nuclei,  is  exactly  similar 
to  the  horny  surface  of  the  epiderm ;  it  terminates  by 
growing  generally  thinner  in  the  upper  third  of  the 
follicle,  about  where  the  excretory  duct  of  the  seba- 
ceous glands  appended  to  the  hair  pours  out  its  secre- 
tion (PI.  XXIV,  fig.  IV.  10;  PL  XXV.  fig.  II.  5)  ; 
P.  XXVII.  fig.  V.  3).  A  very  small  fasciculus  of 
unstriped  muscular  fibres  is  attached  to  the  bottom 
of  the  hair  follicle  externally,  on  the  side  towards 
which  the  hair  inclines  ;  it  passes  obliquely  upwards 
to  the  surface  of  the  true  skin,  where  it  is  inserted ; 
this  is  the  muscle,  by  the  contraction  of  which  the 
hair  is  made  to  straighten  up  at  right  angles  to  the 
surface  of  the  skin,  or,  as  the  phrase  is,  to  "  stand  on 
end." 

The  papilla  which  occupies  the  excavation  at  the 
bottom  of  the  bulb  belongs  to  the  true  skin,  and  is 
more  delicate  in  its  structure  than  its  other  papillae. 
It  contains  several  vessels  which  form  loops  in  its 
interior,  but  its  connexion  with  the  nervous  system  is 
as  yet  unknown  (PL  XXV.  fig.  II.  7). 

Development.  The  hair  and  the  two  epidermic  layers  of  its  fol- 
licle, are  developed  from  a  minute  mass,  or  granula- 
tion of  the  rete  mucosum  which  imbeds  itself  in  the 
surface  of  the  cutis,  whilst  the  two  outer  strata  of  the 
walls  of  the  follicle  are  derived  from  the  formative 
cells  of  the  true  skin.  The  hair  is  developed  all  in 
one  mass,  from  the  little  germ  at  the  bottom  of  its 
follicle ;  the  cells  composing  which,  by  their  various 
transformations,  produce  the  several  elements  of 
which  it  consists,  as  well  as  the  two  epidermic  layers 
by  which  the  follicle  itself  is  lined. 


oj  CHAPTER    IX. 

••{isiu/;*  \q  '>rfl 

Intestinal  Mucous  Membrane. 

THE  mucous  rfnembrane  of  the  alimentary  canal  is  ^eral  struc- 
continuous  with  the  skin,  and,  in  its  essential  consti- 
tuents, possesses  a  similar  structure  ;  thus,  it  consists 
of  two  layers,  one  of  which  corresponds  to,  and  resem- 
bles closely,  the  superficial  stratum  of  the  true-skin — 
the  mucous  membrane  proper ;  the  other,  the  ana- 
logue of  the  cuticle,  and  like  it  composed  of  cells,  is 
the  epithelium.  Nevertheless,  the  varying  shape  and 
disposition  of  its  epithelial  cells,  and  the  peculiar 
modes  of  distribution  of  its  blood-vessels,  as  well  as 
Its  glands,  constitute  a  membrane  $ui  generis  which 
requires  a  description  in  detail. 

A  general  examination  of  this  membrane  shows  at 
once  that  its  appearance  and  structure  are  not  the  same 
throughout.  There  is  evidently  a  considerable  differ- 
ence existing  between  the  several  segments  of  the 
intestinal  tube;  and  in  view  of  this  fact,  and  to  faci- 
litate our  examination  of  the  membrane,  we  shall 
study  its  structure  successively :  1st,  in  the  mouth ;  2d, 
in  the  pharynx  and  oesophagus  ;  3d,  in  the  stomach ; 
4th,  in  the  small,  and  lastly  in  the  large,  intestine. 

The  mucous  membrane  of  the  lips,  cheeks,  palate,  MUCOUS  mem- 

braneof    the 

and  gums,  resembles  exactly  the  superficial  stratum  mouth- 
of  the  true  skin.     It  consists  of  a  layer  furnished  with 
papillae  at  least  as  numerous,  and  of  the  same  shape, 


156  INTESTINAL   MUCOUS    MEMBRANE. 

as  those  of  the  cutis,  and  presenting  a  structure, 
which,  though  perhaps  a  little  more  delicate,  contains 
the  same  elements.  There  is  a  striking  analogy  also 
in  the  distribution  of  its  vessels  and  nerves,  but  up  to. 
the  present  time  no  tactile  corpuscles  have  been 
observed,  except  in  the  papillae  of  the  lips.  On  the 
hard  palate  and  the  gums  the  mucous  layer  is  strongly 
adherent  to  the  periosteum,  with  which,  in  fact,  it  is 
continuous ;  but  on  the  cheeks  and  lips,  it  is  rein- 
forced by  a  delicate  fibrous  layer,  by  which  it  is 
loosely  connected  with  the  subjacent  muscles. 
Epithelium.  Its  epithelial  investment  presents  the  same  general 
physiognomy  as  the  epidermis ;  the  two  deeper  strata, 
corresponding  to  the  rete  mucosum  of  the  cuticle,  are 
absolutely  identical  with  it,  both  in  the  shape  of  their 
cells,  and  in  the  order  of  their  superposition.  The 
superficial  layer  is  likewise  composed  of  scaly  cells, 
but  differing  from  those  of  the  skin  in  the  persistence 
of  their  nuclei. 

Glands.  The  glands  of  this  portion  of  the  alimentary  mu- 
cous membrane  are  all  of  the  clustered  variety ;  they 
occupy  the  sub-mucous  stratum,  sometimes  even,  as  in 
the  cheeks,  being  imbedded  in  the  muscular  layer ;  on 
the  hard  palate  and  gums  they  are  absent. 
MUCOUS  mem-  The  mucous  coat  of  the  inferior  surface  of  the 

brane   of    the 

tongue  is  similar  to  that  of  the  lips,  but  on  its  dorsal 
aspect  it  is  very  different,  both  in  its  external  appear- 
ance, and  in  certain  structural  details. 

On  the  base  of  the  organ  its  mucous  membrane  is 
almost  smooth,  and  sparsely  studded  with  little  len- 
ticular prominences,  with  a  hole  in  the  centre  of  each, 
formed  by  the  projection  of  small  masses  of  subjacent 


INTESTINAL   MUCOUS    MEMBRANE. 

ductless  follicles.     The  rest  of  its  dorsal  surface  is  Ductless. 
thickly  covered  with  very  prominent  papillae,  which 
from  their  variety  in  form,  are  divided  into  three  sets, 
viz :  circumvallate,fungiform,  and  conical,  or  filiform, 
papillae. 

The  papillae  of  the  first  set  are  found  immediately 
in  front  of  the  base  of  the  tongue,  where  they  are 
arranged  in  the  shape  of  the  letter  V.  They  have 
the  shape  of  an  inverted  cone,  with  the  apex  conti- 
nuous with  the  membrane  below,  and  its  base  looking 
upwards  and  free,  and  are  moreover  surrounded  by 
an  elevated  circle  formed  by  the  mucous  membrane, 
which  constitutes  a  sort  of  imperfect  capsule,  in 
which  they  are  almost  concealed  (PL  XXV.  fig. 
III.  1). 

IL\\Q  fungiform  papillae  have  the  same  shape  as  the 
last,  but  are  smaller,  and  project  farther  from  the 
surface  of  the  membrane.  They  are  pretty  uniformly 
distributed  over  the  whole  surface  of  the  tongue, 
being  somewhat  more  numerous  at  its  border  and 
tip. 

The  filiform  papillae,  whose  shape  is  very  well  riiiform  papiiiae. 
indicated  by  their  name,  although  found  everywhere 
on  the  upper  surface  of  the  tongue,  are  more  nume- 
rous in  the  neighborhood  of  its  median  line  than  its 
edges,  where  they  lose  their  characteristic  appear- 
ance (PL  XXV.  fig.  IV.).  Their  direction  is  obliquely 
upwards  and  backwards. 

Each  papilla,  whatever  may  be  its  shape,  is  com-  structure, 
posed  of  the  mucous  membrane  proper,  of  the  sub- 
stance   of    which    it   is  a   projection,    and   covered 
externally   by   epithelium.      In    each   of  the   three 


158  INTESTINAL   MUCOUS   MEMBRANE. 

varieties,  the  inner  or  proper  surface  of  the  papilla 
is  studded  with  secondary  papillae,  in  the  shape  of 
slender  processes  of  variable  length  (PL  XXV.  fig.  III. 
2 ;  fig.  IV.  2).  As  for  the  epithelium,  it  adapts  itself 
accurately  to  the  subjacent  membrane,  presenting  a 
free  surface  which  differs  in  appearance  according  as  it 
corresponds  to  the  localities  occupied  by  the  circurn- 
vallate  and  fungiform  papillae,  or  to  those  of  the  fili- 
form variety ;  in  the  first  case  it  is  perfectly  smooth 
(fig.  III.  3),  but  in  the  latter  it  presents  long  and 
delicate  filaments,  variable  in  length,  and  identical  in 
shape  with  the  secondary  papillae,  the  surface  of 
which  they  cover  (fig.  IV.  3,  4).  It  is  this  epithe- 
lium of  the  filiform  papillae  which  in  some  animals 
assumes  a  horny  character,  and  thus  constitutes  a 
prehensile  organ ;  in  the  pike  its  structure  is  identi- 
cal with  that  of  its  teeth.  The  epithelium  of  the 
tongue  is  identical  with  that  of  the  lips  and  cheeks, 
both  as  regards  the  form  and  disposition  of  its  cells. 

The  filiform  papillae  differ  from  both  of  the  other 
varieties,  not  only  in  their  epithelial  aspect,  but  also 
in  their  relations  to  the  nervous  system ;  thus  the 
nervous  filaments  which  penetrate  them  are  few  in 
number,  and  they  do  not  reach  their  secondary 
papillae.  The  circum  vail  ate  and  fungiform  papillae, 
on  the  contrary,  are  relatively  rich  in  nerve  fibres, 
and  they  can  be  traced  readily  into  their  secondary 
papillae,  where  they  seem  to  terminate  by  free  extre- 
mities ;  Kolliker  has  even  demonstrated  the  presence 
of  tactile  corpuscles  in  the  fungiform  papillae  of  the 
tip  of  the  tongue. 

The  blood-vessels  which  they  receive   are   distri- 


INTESTINAL    MUCOUS   MEMBRANE.  159 

buted  similarly  to  those  of  the  other  papillae  of  the 
buccal  cavity. 

The  glands  of  the  mucous  membrane  of  the  tongue  Glands. 
are  of  two  sorts :  clusters  of  follicles,  and  ductless 
follicles.  The  former,  strictly  speaking,  do  not  belong 
to  the  membrane,  for  they  are  imbedded  in  the  sur- 
face of  the  muscular  tissue  of  the  organ.  They  are 
very  numerous  at  its  base,  where  they  form  a  con- 
tinuous layer  which  extends,  on  either  side,  to  the 
pillars  of  the  fauces,  and,  in  front,  encroaches  upon 
its  papillary  surface.  Those  which  are  situated  pos- 
teriorly upon  the  edges  of  the  tongue,  and  upon  the 
under  surface  of  its  tip,  are  also  concealed  amongst 
the  superficial  muscular  fibres  of  the  organ,  and  are 
connected  with  its  mucous  membrane  by  their  excre- 
tory ducts  only,  which  pierce  it,  and  open  either  at 
the  bottom  of  the  sulti  on  its  edges,  or  on  either 
side  of  the  frcenum. 

The  ductless  follicles  at  the  base  of  the  tongue  Ductless  glands, 
constitute  the  little  lenticular  eminences  which  are 
found  in  that  region.  Upon  the  summit  of  each  lit- 
tle projection  is  an  orifice,  visible  to  the  naked  eye, 
which  leads  into  a  flask-shaped  cul-de-sac,  the  walls  of 
which  are  continuous,  and  identical  in  structure,  with 
the  mucous  lining  of  the  organ.  The  network  of 
vessels  which  immediately  surrounds  this  orifice 
is  closer  and  richer  than  elsewhere  in  its  vicinity 
(PL  XXV.  fig.  V.).  The  walls  of  the  cavity  are 
reinforced  by  a  dense  lamina  of  connecting  tissue,  in 
the  substance  of  which  are  imbedded  about  twenty 
minute  spherical  bodies,  of  the  same  size  as  the  soli- 
tary glands  of  the  intestine,  and  identical  with  them 


160  ,    INTESTINAL    MUCOUS    MEMBKANE. 

in  structure  (vide  ut  supra}.  These  follicles  present 
no  trace  of  an  excretory  duct,  or  any  visible  external 
opening ;  the  existence  of  the  central  orifice  on  the 
surface  of  the  mucous  covering  of  the  eminence 
which  they  form,  has  led  to  mistakes  on  this  point, 
but,  as  we  have  already  seen,  this  opens  only  into  a 
cul-de-sac. 

Tonsils.  The  tonsils  are  composed  of  an  aggregation  of 
ductless  follicles  identical  with  those  just  described ; 
they  are  therefore  compound  ductless  glands.  The 
excavations  which  we  see  upon  their  free  convex  sur- 
faces are  simple  blind  cavities,  sometimes  containing 
masses  of  whitish  material  of  a  disagreeable  odor, 
and  consisting  of  debris  of  epithelium  in  a  state  of 
partial  fatty  degeneration. 

The  lymphatics  of  the  cavity  of  the  mouth  are 
very  numerous,  especially  those  of  the  mucous  mem- 
brane of  the  tongue.  They  appear  to  take  their 
origin  immediately  beneath  its  epithelial  layer,  and 
communicate  with  the  cervical  lymphatic  glands. 

The  papillae  of  the  mucous  membrane  of  the  pha- 
rynx are  smaller,  and  less  numerous,  than  those  of 
the  mouth.  Its  epithelium,  in  strata,  resembles  that 
of  the  buccal  cavity,  only  it  is  to  be  noticed  that  in 
the  upper  portion,  or  vault,  of  the  pharynx,  it  is  pro- 
vided with  ciliated  cells,  In  the  deeper  layers  of  the 
membrane  proper  are  numerous  ductless  glands,  and 
clusters  of  follicles  ;  the  first  are  found  only  in  the 
upper  part  of  the  pharynx,  whilst  the  mucous  folli- 
cles exist  in  all  parts  of  the  membrane.  Its  blood- 
vessels are  numerous,  and  are  similarly  distributed  to 
those  of  the  walls  of  the  cavity  of  the  mouth.  Its 


s 


INTESTINAL    MUCOUS    MEMBRANE.  161 

lymphatics  run  into  the  deeper  cervical  glands.  The 
nerves  are  very  numerous,  and  seern  to  terminate  by 
free  extremities. 

In  the  mucous  membrane  of  the  oesophagus  there 
are  a  great  many  conical  papillae,  but  otherwise  its 
structure  is  the  same  as  that  of  the  pharynx.  It  has 
no  ductless  glands,  and  its  mucous  follicles  are  not 
very  numerous.  Its  blood-vessels,  by  no  means  so 
abundant  as  those  of  the  pharynx,  have  no  peculi- 
arities in  regard  to  their  distribution.  Its  lymphatics 
communicate  with  the  deep  glands  of  the  lower  -part 
of  the  neck,  and  with  those  of  the  posterior  medi- 
astinum. It  is  freely  supplied  with  nerves,  but  their 
mode  of  termination  is  as  yet  undetermined. 

The  mucous  membrane  of  the  pharynx  and  ceso- 
phagus  is  everywhere  connected  by  its  attached  sur- 
face to  a  thick  stratum  of  muscular  tissue  ;  in  the 
pharynx  this  is  formed  by  its  constrictor  muscles,  and 
in  the  cesophagus  by  two  layers,  of  which  the  fibres 
of  the  inner  are  circular,  and  the  outer,  longitudinal. 
The  muscular  walls  of  the  pharynx  are  composed 
exclusively  of  striped  fibres,  but  in  the  cesophagus 
this  is  true  only  of  its  upper  part  ;  below,  its  mus- 
cular fibres  are  non-striated.* 

The  mucous  membrane  of  the  stomach  is  softer  and  Gasti:ic  mucous 

membrane. 

*  According  to  Todd  and  Bowman  (Physiological  Anatomy,  Lond. 
1856,  vol.  II.  p.  188),  striped  muscular  fibres  can  be  traced  as  far  as  the 
diaphragm,  in  the  muscular  coat  of  the  oesophagus  ;  and  according  to 
Sharpey  and  Quain  (Elements  of  Anatomy,  5th  Ed.,  Lond.,  1848,  vol. 
II.  p.  1015),  "they  have  been  traced  throughout  its  whole  length,  and 
even,  it  is  said  (Ficinus),  upon  the  cardiac  end  of  the  stomach."  This  is 
also  stated  by  Cruveilhier,  on  the  authority  of  Valentin  and  Ficinus  (Ana- 
tomy, 1st  Am.  ed.  New  York,  1844,  foot  note,  p.  323.  —  (Ed.) 


162  INTESTINAL   MUCOUS   MEMBRANE. 

thicker  than  that  of  the  oesophagus ;  it  is  of  a  pale 
rose  color  whilst  the  organ  is  empty,  but  becomes 
red  during  digestion.  When  relaxed,  it  is  thrown 
into  a  great  number  of  wrinkles  (rug  of),  which  are 
effaced  when  the  stomach  is  distended.  Its  surface 
is  smooth :  throughout  its  whole  extent,  except  near 
the  cardiac  orifice,  where  there  are  papillae  similar  to 
those  of  the  oesophagus  (Berres*),  and  at  the  pylorus, 
where  flattened  villi  are  found  (Krausef ).  Its  epi- 
thelium consists  of  a  single  layer  of  cylindrical  cells, 
similar  to  those  of  the  intestine.  The  reddish  tint, 
which  it  derives  from  the  subjacent  layers  of  mus- 
cular tissue,  contrasts  strongly  with  the  whiter  color 
of  the  epithelium  of  the  oesophagus ;  the  serrated 
line,  at  the  cardiac  orifice  of  the  stomach,  which 
marks  the  union  of  these  two  layers  of  epithelium,  is 
very  distinct. 

Glands.  The  surface  of  the  gastric  mucous  membrane  is 
pierced  by  an  infinite  number  of  minute  holes,  from 
iio-th  to  Voth  of  a  line  in  diameter  ;  these  are  the  ori- 
fices of  the  gastric  glands  (PL  XXV.  fig.  VII.  1). 
These  glands  all  belong  to  the  tubular  variety,  but 
some  of  them  are  single,  and  others  compound.  The 
former  (the  glands  which  secrete  gastric  juice)  occupy 
nearly  the  whole  extent  of  the  membrane,  and  are 
the  same  in  form  and  structure  as  the  follicles  of  Lie- 
berkuhn  already  described.  As  for  the  compound 

*  Joseph  Berres,  Professor  of  Anatomy  in  the  University  of  Vienna, 
predecessor  and  preceptor  of  Hyrtl,  the  present  occupant  of  the  same 
chair.  Berres  died  in  1846,  leaving  an  unfinished  work  on  Microsco- 
pical Anatomy. — (Ed.} 

t  C.  F.  J.  Krause,  Professor  of  Anatomy  at  Hanover. — (Ed.) 


INTESTINAL   MUCOUS   MEMBRANE.  163 

gastric  follicles,  one  portion  of  them  occupies  the 
vicinity  of  the  cardiac  orifice  (those  secreting  pepsin), 
whilst  the  other  (consisting  of  mucous  glands)  is 
found  near  the  pylorus ;  both  have  been  already 
described  (PL  XXV.  fig.  VIII. ;  PL  XXVI.  fig.  I). 

The  mucous  coat  of  the  stomach  is  rich  in  blood- 
vessels  which,  first  supplying  its  glands,  terminate 
nearer  its  surface  in  a  very  regular  capillary  network, 
the  largest  meshes  of  which  surround  their  orifices. 
Its  Jyinphatic  vessels  communicate  with  the  little 
glands  which  lie  along  the  greater  or  lesser  curvatures 
of  the  organ.  The  mode  of  distribution  and  ultimate 
termination  of  the  very  numerous  nervous  branches 
which  it  receives  from  the  great  sympathetic  and 
pneumogastric,  are  not  clearly  demonstrated. 

The  mucous  membrane  of  the  small  intestine,  which  smaii  intestine. 
in  all  the  essential  points  of  its  structure  resembles 
that  of  the  stomach,  differs,  from  it,  nevertheless,  both 
in  the  appearance  of  its  surface,  and  in  the  character 
of  certain  of  its  glands.  Upon  its  free  surface  two 
species  of  prominences  are  noticeable — valvulce  con- 
niventes  and  villi.  The  former  are  long  semilunar 
folds,  formed  by  the  plaiting  of  the  membrane  upon 
itself;  their  direction  is  perpendicular  to  the  axis  of 
the  canal,  and  each  occupies  the  half  or  two-thirds  of 
its  circumference ;  they  slope .  off  to  a  point  at  either 
extremity,  and  are_  connected  to  each  other  by  little 
oblique  folds.  They  are  very  large  and  numerous  in 
the  duodenum,  where  they  overlap  each  other  like 
shingles  on  the  roof  of  a  house,  and  in  such  a  manner 
that  their  free  edges  look  downwards.  As  we  trace 
them  downwards,  following  the  surface  of  the  bowel, 


164  INTESTINAL    MUCOUS    MEMBRANE. 

they  gradually  and  regularly  diminish  both  in  num- 
ber and  in  size,  until,  in  the  lower  part  of  the  ileum, 
they  are  recognisable  only  by  a  faint  thickened  line. 
The  villi  of  the  small  intestine  are  minute  pro- 
cesses, analogous  to  the  papillae  of  the  tongue,  but 
more  delicate  in  their  proportions.  The*  best  idea  of 
their  shape,  number,  and  mode  of  arrangement,  is  to 
be  got  by  placing  a  piece  of  the  mucous  membrane 
under  water,  and  examining  it  with  a  magnifying 
glass,  or  a  microscope  with  a  low  power.  They  are 

>  seen  to  occupy  the  whole  extent  of  the  surface  of  the 

membrane,  and  to  be  more  numerous  in  the  duo- 
denum and  jejunum,  than  in  the  ileum  /  they  are  seen 
also  to  assume  two  principal  forms — the  flat,  or  val- 
vular, and  the  conical.  The  flat  villi  are  principally 
found  in  the  upper  portion  of  the  small  intestine; 
they  are  simple  and  solitary,  or,  by  running  into  each 
other,  become  compound,  in  which  case  they  resemble 
minute  valvulce  conniventes  (PL  XXVI.  fig.  II.  2,  3). 
The  conical  villi  are  found  everywhere  throughout 
the  small  intestine,  but  they  exist  in  larger  proportion 
in  the  ileum  (fig.  III.  1).  In  some  instances,  instead 
of  terminating  in  a  point,  their  apices  are  slightly 
bulbous  (PL  XXVI.  fig.  XII.) ;  their  average  height 
is  from  one-fourth  to  one-half  a  line,  and  their  dia- 
meter from  one-sixteenth  to  one-fourth  of  a  line. 

structure  of  the       Whatever  may  be  the  form  of  a  villus  its  structure 

villi.  .  J 

is  always  the  same,  and,  in  examining  it  from  its  surface 
inwards  we  find,  first :  a  single  lamina  of  epithelium 
which,  on  a  perfectly  fresh  specimen  which  has  not 
been  roughly  handled,  presents  the  appearance  of  a 
mosaic,  upon  the  surface  of  which  an  unbroken  layer 


INTESTINAL   MUCOUS   MEMBKANE.  165 

of  amorphous  material  has  been  applied  (PL  XXVI. 
fig.  TV.  1,  2,  3 ;  fig.  V.).  By  breaking  up  this  layer 
of  epithelium  we  recognise  the  elements  of  which  it 
is  composed,  viz.  conical  cells,  the  summits  of  which 
rest  upon  the  surface  of  mucous  membrane,  whilst 
their  bases  are  directed  outwards  and  free,  or  rather 
covered  by  the  amorphous  substance  already  men- 
tioned, which  adheres  to  them  very  closely  (fig.  VI.). 
It  is  only  in  perfectly  fresh  and  recent  specimens  that 
the  cells  are  found  covered  by  this  amorphous  coat- 
ing; it  disappears  entirely  in  from  twelve  to  twenty- 
four  hours  after  death  (PL  I.  fig.  VI.).  The  contents 
of  a-  cell  consist  of  fine  granules,  and  its  nucleus,  which 
is  oval  in  shape,  is  usually  nearer  to  its  apex  than  its 
base  ;  their  mean  length  is  Toth  of  aline,  their  breadth 
232<l  of  a  line,  and  the  diameter  of  their  nuclei  a^th 
of  a  line.  The  epithelium  which  covers  the  mucous 
membrane  in  the  intervals  between  the  villi  has  also 
the  appearance  and  structure  of  that  first  described. 
Immediately  beneath  the  layer  of  epithelium  is  the 
surface  of  the  naked  villus,  or  papilla,  and  this  is 
formed  by  a  structureless  basement  membrane  similar 
to  that  already  noticed  upon  the  surface  of  the  papil- 
lary layer  of  the  true  skin. 

Beneath  this  simple  membrane  is  a  close  network  of 
capillary  vessels  formiDg  a  sort  of  hollow  bulb  which 
encloses  the  remainder  of  the  villus  (PL  XXVI.  fig. 
VIII.)  ;  this  capillary  plexus  seems  to  communicate 
more  freely  with  the  venous  than  with  the  arterial  sys- 
tem, for  it  is  much  easier  to  fill -it  with  fine  injection 
from  the  venaportce  than  from  the  abdominal  aorta. 
In  the  centre  of  the  villus  is  a  large  hollow  canal  (T<T o  th 


166  INTESTINAL   MUCOUS    MEMBKANE. 

to  Tsad  of  a  line  in  diameter)  ending  by  a  blind  and 
somewhat  bulbous  extremity;  this  is  the  origin  of  a 
lacteal  vessel  (PL  XXVII.  fig.  VI.  2).  The  situation 
of  this  solitary  vessel  in  the  centre  of  the  villus, 
compared  with  the  position,  on  its  surface,  of  the 
capillary  plexus,  so  rich  in  blood-vessels,  should  teach 
us  that  the  activity  of  its  function  as  an  absorbent  is 
subordinate  to  that  of  the  elements  by  which  it  is 
surrounded.  The  remainder  of  the  villus  consists  of 
a  material  faintly  fibrillated  rather  than  amorphous, 
which  encloses  a  number  of  oval  nuclei,  the  meaning 
of  which  is  unknown  (PL  XXVI.  fig.  VII.  3). 
Around  the  outer  surface  of  the  lacteal,  non-striated 
fibres  of  muscular  tissue  are  sometimes  found,  running 
parallel  with  the  axis  of  the  villus.  We  know  nothing 
of  the  connexion  of  the  nervous  system  with  the  villi. 
The  glandular  apparatus  of  the  small  intestine  is 
composed  of  clusters  of  follicles,  tubular  glands,  and 
ductless  follicles. 

Glands  of  Brun-  Brunue^ s  glands  are  clusters  of  follicles,  situated 
deeply  in  the  mucous  membrane,  or  rather  in  the  sub- 
mucous  layer  of  connecting  tissue.  They  are  little 
yellowish-white  granules,  averaging  one-half  a  line  in 
diameter,  and  precisely  similar  in  structure  to  the 
salivary  glands ;  they  are  provided  with  a  single 
layer  of  polygonal  epithelium,  and  they  secrete  an 
alkaline  fluid  in  which  no  organic  element  is  disco- 
verable (PL  XXVI.  fig.  IX.).  These  glands  are  only 
found  in  the  duodenum. 

Glands  of  Lieber-  ^he  tubular  glands,  or  follicles  of  Lielerlvuhn, 
placed  side  by  side  like  quills  in  a  bundle,  constitute 
a  secretory  apparatus  which  occupies  the  whole 


INTESTINAL   MUCOUS    MEMBRANE.  167 

extent  of  the  small  intestine.  On  examining  the  sur- 
face of  a  piece  of  mucous  membrane  under  water, 
with  a  low  magnifying  power,  we  recognise  a  great 
number  of  minute  holes,  which  are  nothing  more  than 
the  orifices  of  these  glands  (PL  XXVI.  fig.  II.  4 ;  fig. 
III.  2  ;  fig.  XII.  3).  Their  structure  has  been  already 
studied. 

The  ductless  follicles,  with  the  structure  of  which  Ductless  glands 
we  are  already  familiar,  are  either  solitary  or  aggre- 
gated in  groups,  and  in  either  case  are  imbedded  in 
the  sub-mucous  tissue.  As  solitary  glands,  they  are 
scattered  throughout  the  whole  extent  of  the  mucous 
coat  of  the  jejunum  and  ileum.  It  is  only  in  excep- 
tional cases  that  they  are  found  in  the  duodenum. 
When  collected  in  groups  they  constitute  the  essen- 
tial element  of  the  patches  of  Peyer.  These  latter, 
very  variable  in  number,  are  usually  seated  in  the 
ileum  and  lower  half  of  \\\e  jejunum  y  sometimes,  but 
very  rarely,  they  are  found  higher  up,  and  even  in 
the  duodenum.  They  are  oval  in  shape,  with  their 
Long  diameters  parallel  with  the  axis  of  the  intestinal 
canal,  and  are  seated  opposite  to  the  attachment  of 
the  mesentery.  The  surface  of  a  patch  of  Peyer  is 
studded  with  villi,  and  also  with  the  minute  orifices 
of  Lieberkuhn's  follicles,  as  elsewhere  on  the  surface 
of  the  intestinal  mucous  membrane  ;  but  besides  these 
it  presents  a  number  of  larger  depressions  (one-half  a 
line  in  measurement),  at  the  bottom  of  each  of  which 
is  a  little  prominence  which  corresponds  to  the  posi- 
tion of  a  ductless  gland.  These  are  perfectly  blind 
depressions,  situated  just  over  the  glands,  and  this 
relation  between  the  two  has  given  rise  to  the  false 


168  INTESTINAL    MUCOUS    MEMBKANE, 

impression  that  these  glands  possess  outlets.  The 
solitary  glands,  instead  of  underlying  a  depression,  on 
the  contrary  cause  a  slight  projection  of  the  membrane 
which  covers  them,  which,  with  this  exception,  pre- 
sents the  same  appearance  as  elsewhere  (PL  XXVI. 
fig.  XII.  1). 
MUCOUS  mem-  The  mucous  membrane  of  the  large  intestine  is 

brane  of  large  in-  .... 

smooth  and  destitute  of  villi,  and  in  this  respect 
resembles  that  of  the  stomach.  Its  glandular  appa- 
ratus comprises  follicles .  of  Lieberkuhn  and  solitary 
glands,  identical  with  those  of  the  small  intestine, 
only  it  is  to  be  noticed  that  its  solitary  glands  corres- 
pond in  situation  always  with  a  depression  on  the 
surface  of  the  membrane,  as  we  have  seen  in  the 
patches  of  Peyer  (PL  XXVI.  fig.  XV.).  Its  vessels 
present  the  same  appearance  and  distribution  as  those 
of  the  stomach ;  in  relation  to  its  nerves  nothing  pre- 
cisely is  known. 

The  intestinal  mucous  membrane  of  the  abdomen 
is  connected  to  the  muscular  coat  of  the  canal  by  a 
rather  lax  stratum  of  connecting  tissue  (sub-mucous 
layer,  fibrous  coat,  nervous  coat)  in  which  are  im- 
bedded the  glands  of  Brunner,  the  ductless  follicles — 
solitary  and  aggregated,  and  the  sub-mucous  network 
of  blood-vessels. 

The  development  of  the  glands  of  the  intestine 
takes  place  by  means  of  minute  granulations  which 
spring  from  its  epithelial  layer,  and  in  this  respect 
presents  a  close  analogy  with  the  mode  of  develop- 
ment of  the  glands  of  the  skin. 

The  mode  in  which  the  epithelium  of  the  intestine 
is  reproduced  is  unknown  at  the  present  time  ;  it  is 


* 


INTESTINAL   MUCOUS   MEMBRANE.  169 

probably  accomplished  by  endogenous  vegetation  and 
subsequent  cleavage  of  its  cells;  the  presence  of 
nuclei  in  a  large  proportion  of  these  elements  renders 
it  probable  that  the  process  is  thus  effected. 


CHAPTER  X. 
Organs  of  Sense. 

SECT.  I.  THE  EYE. — The  apparatus  of  vision  com- 
prises the  globe  of  the  eye,  or  the  organ  of  sight  pro- 
perly so  called  ;  its  organ  of  protection,  the  eyelids  ; 
and  its  motor  and  lachrymal  apparatus.  As  the  two 
latter  present  no  features  of  special  histological 
interest,  we  shall  omit  their  consideration. 
Eyelids  The  several  layers  of  tissue  which  enter  into  the 
composition  of  the  eyelids,  proceeding  from  without 
inwards,  are :  the  skin,  the  orbicular  muscle,  the 
fibrous  stratum,  and  finally,  the  mucous  membrane. 

The  skin  is  exceedingly  delicate,  but  otherwise  it 
presents  the  same  structure  as  elsewhere.  Situated 
deeply  in  its  substance,  and  near  the  free  edges  of  the 
eyelids,  we  find  the  hair-follicles  of  the  cilia  or  eye- 
lashes, surrounded  by  their  sebaceous  glands  (PL 
XXVII.  fig.  V.).  The  orbicular  muscle  of  the  eye- 
lids belongs  to  the  class  of  striped  muscles  (PL 
XXVII.  fig.  II.).  The  fibrous  stratum,  very  thin  at 
the  bases  of  the  eyelids,  becomes  more  dense  towards 
their  free  edges,  where  it  forms  the  tarsal  cartilages. 
These  are  composed  of  connecting  tissue  very  much 
condensed,  and  studded  with  plaematic  cells.  We 
search  in  vain  in  this  stratum  of  fibrous  tissue  for  car- 
tilage cells,  or  at  least,  they  are  so  rarely  encountered 
that  they  cannot  be  regarded  as  constituting  one  of 


OKGATCS    OF   SENSE. 


Ill 


its  normal  elements.  "We  must  give  up  the  idea 
therefore  that  these  dense  laminae  consist  of  fibro- 
cartilage,  for  they  have  only  its  appearance,  without 
possessing  its  structure.  On  their  deep  surfaces  there 
are  from  twenty  to  thirty  parallel  grooves,  which 
accommodate  the  Meibomian  glands  (PL  XXVII. 

%.  in.). 

The  mucous  membrane,  or  conjunctiva,  consists  of 
quite  a  dense  layer  of  connecting  tissue,  the  ocular 
surface  of  which  is  studded  with  numerous  papillae 
analogous  to  those  of  the  skin  ;  its  epithelium,  which 
is  stratified,  resembles  that  of  the  skin  and  mucous 
membrane  of  the  mouth  (Pi.  XXVIII.  fig.  II.  5). 
This  membrane,  as  is  well  known,  is  reflected  from 
the  eyelids  upon  the  globe  of  the  eye,  to  which  it 
becomes  intimately  attached ;  tracing  it  here  to  the 
circumference  of  the  cornea,  it  is  to  be  remarked  that 
its  deep  layer  becomes  gradually  thinner,  and  ceases 
suddenly  by  becoming  inserted  into  the  amorphous 
border  which  surrounds  the  anterior  margin  of  the 
cornea  (PL  XXVIII.  fig.  II.  4),  whilst  its  epithelial 
layer  continues  its  course  and  covers  the  whole  ante- 
rior surface  of  the  cornea  (fig.  I.  7 ;  fig.  II.  5).  The 
vessels  and  nerves  of  the  cornea  present  no  peculia- 
rities worthy  of  note. 

Globe  of  the  Eye. — The  first  proper  coat  of  the  eye- 
ball  is  formed  posteriorly  by  the  scierotica,  and  in 
front,  by  the  cornea.  The  scierotica  is  an  exceeding- 
ly dense  membrane,  thicker  anteriorly  and  posteriorly 
than  around  the  centre  of  the  eye-ball,  and  consisting 
of  a  close  tissue  of  connective  and  elastic  fibres.  An- 
teriorly this  membrane  adheres  very  intimately  to 


172  OKGANS    OF   SENSE. 

the  conjunctiva,  which  is  distinguishable  from  it  by 
the  greater  looseness  of  its  texture,  and  by  the  larger 
number  of  plasmatic  cells  which  it  contains  (PL 
XXVIII.  fig.  II.).  Its  deep  surface  is  closely  attached 
to  the  dioroid  membrane  only  at  its  anterior  limits, 
where  it  gives  insertion  to  the  ciliary  muscle  (fig. 
IV.  1).  The  canal  of  Schlemm  is  also  found  along 
the  line  which  limits  the  sclerotica  in  front,  forming 
a  tunnel  near  the  deep  surface  of  the  membrane  (fig. 
IV.  2). 

The  cornea  is  composed  of  an  amorphous  funda- 
mental substance,  which  contains  a  great  quantity  of 
plasmatic  cells  (fig.  I.  2  ;  fig.  III.  2).  These  are  dis- 
posed very  regularly  in  concentric  lines  running 
parallel  with  the  two  surfaces  of  the  cornea.  When 
very  dilute  acetic  acid  is  applied  to  prepared  speci- 
mens of  the  cornea,  the  stellate  shape  of  these  cells, 
and  the  numerous  anastomoses  between  their  prolon- 
gations, are  rendered  perfectly  visible,  and  their 
appearance  recalls  vividly  the  structure  of  bone. 
But  if  the  acid  should  be  too  much  concentrated  the 
prolongations  of  the  cells  become  pale,  and  their 
bodies  alone  remain  visible  (PL  II.  fig.  V.).  The 
front  surface  of  the  cornea  is  limited  by  a  thin  edge 
which,  in  a  section,  forms  an  amorphous  border  from 
aloth  to  aioth  of  a  line  in  thickness,  the  anterior  mar- 
gin being  in  contact  with  the  epithelium  of  the  con- 
junctiva (PL  XXVIII.  fig.  II.  3).  Its  posterior  sur- 
face also  forms  an  amorphous  border,  of  the  same 
thickness  as  the  latter ;  it  is  continuous,  by  means  of 
fibrous  tissue,  with  the  anterior  margin  of  the  scle- 
rotica and  the  ciliary  muscle  (fig.  III.  4 ;  fig.  IV.). 


OEGANS   OF   SENSE.  173 

It  is  invested  by  a  single  layer  of  pavement  cells, 
which  is  reflected  upon  the  anterior  surface  of  the 
iris,  and  ceases  at  the  margin  of  the  ptfpil  (membrane 
of  Demoins,  of  Descemet,  fig.  III.  4,  5). 

There  is  no  distinct  line  of  demarcation,  as  inspec- 
tion by  the  unassisted  eye  would  lead  us  to  suppose, 
between  the  cornea  and  sclerotica.  The  two  mem- 
branes blend  insensibly  with  each  other  (fig.  I.  3). 
The  fibres  of  the  sclerotica  become  rarified  as  they 
approximate  the  corneal  margin,  and  they  can  be 
clearly  seen  to  be  continuous  with  the  branches  of  its 
plasmatic  cells  (fig.  II.  1,  2). 

The  sclerotica  has  but  few  vessels,- and  hardly  any  vessels  and 

'  J  J     nerves. 

nerves.  There  are  no  blood-vessels  in  the  cornea; 
its  network  of  plasmatic  cells  affords  ample  circulation 
for  the  nutritive  fluid.  Its  nerves  are  very  numerous, 
and  form  a  rich  web  of  filaments  which  are  found 
chiefly  near  its  anterior  surface  (Kolliker)  ;  according 
to  some  authorities  they  terminate  by  free  extre- 
mities. 

The  second  tunic  of  the  eye-ball  is  formed  poste- 
riorly  by  the  choroid,  and  in  front  by  the  iris.  The 
choroid  coat  lines  the  internal  surface  of  the  sclero- 
tica, very  accurately,  and  is  continuous  in  part  with 
the  iris,  without  any  line  of  demarcation  (PL  XXVIII. 
fig.  I.  11,  12).  It  is  loosely  .connected  by  its  external 
surface  to  the  sclerotica,  by  means  of  the  ciliary  ves- 
sels and  nerves,  and  an  occasional  very  delicate  fasci- 
culus of  fibrous  tissue ;  its  brownish-black  color  is 
explained  by  the  presence  of  a  layer  of  irregularly 
branching  cells  filled  with  pigment  granules  (PL  II. 
fig.  II.  1,  2,  3).  Its  internal  surface  is  likewise  covered 


174  OEGANS    OF   SENSE. 

by  a  layer  of  pigment  cells,  but  these  are  regular 
polygons,  more  numerous,  and  containing  a  larger 
quantity  of  pigment,  than  those  last  mentioned  (PL 
II.  fig.  I.)  ;  this  layer  has  no  connexion  with  the 
retina,  with  which  it  is  in  contact.  Between  these 
two  layers  of  pigment  cells  is  the  proper  substance  of 
the  choroid  membrane. 

cmary  muscles.  The  greyish  thickened  ring  of  tissue  which  forms 
the  limit,  anteriorly,  of  the  choroid,  and  by  which  it 
is  firmly  united  to  the  sclerotica,  is  muscular  in  its 
nature,  and  constitutes  the  principal  bulk,  or  body,  of 
the  ciliary  muscle  ;  it  is  also  described  as  the  ciliary 
circle  or  ring,  ciliary  ligament,  and  ciliary  ganglion. 
On  its  surface  it  appears  to  consist  of  non-striated 
muscular  fibres,  parallel  in  their  direction  with  the 
antero-posterior  axis  of  the  globe  of  the  eye.  Ante- 
riorly it  grows  thin  (jVd  of  a  line  in  thickness),  and 
is  inserted,  at  first,  into  the  inferior  wall  of  the  canal 
of  Schlemm,  and,  a  little  farther  on,  into  the  posterior 
extremity  of  a  fasciculus  of  fibres  which  is  continuous 
with  the  amorphous  border  of  the  cornea,  and  adhe- 
rent also  to  the  circumference  of  the  iris,  called  the 
pectiniform  ligament  (PL  XXVIII.  fig.  IV.  3).  The 
deeper  portions  of  the  ciliary  muscle,  which  are  in 
relation  with  the  ciliary  processes,  consist  of  inter- 
laced muscular  fibres;  at. least  this  is  the  inference  to 
be  drawn  from  the  variable  aspect  presented  by  the 
muscular  nuclei  of  the  part  in  a  section  (fig.  IV.  5,  6). 
Posteriorly,  the  muscle  gives  off  longitudinal  fasciculi 
which  extend  as  far  as  the  middle  of  the  choroid,  and 
anteriorly,  it  presents  similar  fasciculi  of  fibres  which 
penetrate  the  iris,  and  converge  towards  the  pupil. 


ORGANS    OF   SENSE.  175 

The  ciliary  vessels  which  traverse  the  muscle  become 
intimately  amalgamated,  so  to  speak,  with  its  sub- 
stance, and  thus  constitute  an  erectile  apparatus 
(Kouget).  The  posterior  half  of  the  choroid  is  com- 
posed of  vessels  united  together  by  very  delicate  con- 
necting tissue,  which  contains  some  plasmatic  cells. 

Each  of  the  surfaces  of  the  iris  is  covered  by  a 
simple  layer  of  epithelium.  That  upon  its  anterior 
aspect  has  been  already  examined  (fig.  III.  5)  ;  the 
epithelium  upon  its  posterior  surface  (uvea)  is  com- 
posed of  polygonal  pigment  cells  similar  to  those  of 
the  choroid.  In  addition  to  the  blood-vessels  con- 
tained in  the  iris,  we  find  also,  in  the  substance  of 
this  membrane,  a  ring  of  muscular  fibres  surrounding 
the  pupil  and  connected,  by  its  circumference  with 
the  converging  fibres  of  the  ciliary  muscle,  and  finally 
a  web  of  connecting  tissue  full  of  plasmatic  cells.  In 
most  eyes,  but  especially  in  those  of  dark  color,  the 
majority  of  these  cells  contain  pigment  granules. 

The  nerves  of  the  choroid  coat  and  iris  (ciliary 
nerves)  are  very  numerous,  and  seem  intended  for 
the  supply  of  the  muscular  apparatus  belonging  to 
these  membranes. 

The  retina,  which  constitutes  the  third  coat  of  the 
eye-ball,  is  coextensive  with  the  choroid  coat,  beneath 
which  it  lies.  At  the  entrance  of  the  optic  nerve  it 
is  thicker  than  elsewhere  ;  in  fact  a  slight  prominence 
is  perceptible  at  this  point,  which  has  been  designated 
as  the  papilla  of  the  retina.  At  the  posterior  extre- 
mity of  the  antero-posterior  axis  of  the  globe,  and 
consequently  to  the  outer  side  of  the  pupil,  there  is, 
upon  the  surface  of  the  retina,  an  elongated  depres- 


176  OEGAJTS    OF   SENSE. 

sion  of  a  light  yellowish  color — the  yellow  spot  of 
Scemmering.  As  we  trace  it  forwards,  the  retina  grows 
thinner,  and  its  anterior  border  corresponds  with  the 
outer  circumference  of  the  iris ;  its  nervous  matter, 
however,  can  be  traced  no  farther  than  the  com- 
mencement of  the  ciliary  processes,  where  it  ter- 
minates abruptly,  by  a  serrated  margin  (or a  serrata). 

The  researches  of  H.  Muller*  demonstrate  the 
structure  of  the  retina  to  be  as  follows  : 

Its  outer  layer  is  made  up  of  little  "  club-shaped 
rods"  arranged  closely  side  by  side  so  as  to  form  an 
uninterrupted  lamina — the  membrana  Jacolri.  Their 
direction  is  perpendicular  to  the  surface  of  the  retina, 
and  their  shape,  as  their  name  indicates,  is  cylindri- 
cal; but  some  of  them  enlarge  at  their  outer  extremi- 
ties, so  as  to  assume  a  conical  form.  These  latter  are 
fewer  in  number  than  the  club-shaped  bodies  first 
mentioned,  and  are  quite  uniform  in  their  distribu- 
tion, with  this  exception,  that  they  alone  constitute 
the  whole  thickness  of  Jacob's  membrane  where  it 
passes  over  the  yellow  spot  of  Soemmering.  The 
internal  extremities  of  these  club-shaped  bodies  taper 
off,  and  each  one  of  them,  becomes  continuous  with  a 
fibre  (fibre  of  Muller),  which  traverses  the  whole 
thickness  of  the  retina.  In  its  course  this  fibre  pre- 
sents three  distinct  enlargements  :  the  first  is  situated 
at  its  outer  extremity,  just  where  it  is  joined  by  the 
corresponding  club-shaped  body;  the  second  at  its 
middle,  and  the  third  at  its  internal  extremity.  The 
first  corresponds  to  the  external  granular  layer,  which 

*  Professor,  or  Lecturer,  on  Anatomy  in  the  University  of  "Wurz- 
burg,  Bavaria. — (Ed.) 


OEGANS    OF   SENSE. 


is  made  up  entirely  by  these  external  enlargements 
or  granules,  the  second  to  the  internal  granular  layer, 
and  the  third  series  of  enlargements  is  intimately 
mingled  with  the  fibres  of  the  optic  nerve,  and  with 
them  constitutes  the  fibrous  stratum  of  the  retina. 
The  external  and  middle  enlargement  of  the  fibres  of 
Miiller  are  composed  of  cells  ;  the  internal  enlarge- 
ment consists  of  a  homogeneous  mass,  with  a  depres- 
sion upon  its  inner  surface,  by  which  it  rests  upon  a 
very  delicate  structureless  lamella  (2  oVo-th  of  a  line  in 
thickness)  which  constitutes  the  limitary  membrane 
of  the  retina  within. 

On  the  internal  surface  of  the  internal  granular 
layer,  and  consequently  between  it  and  the  fibrous 
layer,  is  a  stratum  composed  of  multipolar  or  caudate 
nerve  cells  (nervous  layer)  ;  and  the  fibrous  layer,  as 
already  stated,  consists  of  an  expansion  of  the  fibres 
of  the  optic  nerve.*  These  latter,  as  they  run  for- 
wards towards  the  anterior  border  of  the  retina, 
curve  outwards  to  unite  themselves  with  the  pro- 
longations of  the  nerve-cells,  which,  in  their  turn, 
send  an  anastomosing  fibre  to  each  of  the  middle 
enlargements  on  the  fibres  of  Miiller.  In  the  centre 
of  the  yellow  spot  of  Scenamering  we  find  nothing  but 
nerve-cells  within  the  meinbrana  Jacobi. 

In  reviewing  what  has  just  been  said  in  relation  to 
the  arrangement  of  the  diverse  elements  composing 
the  retina,  it  is  obvious  that  this  membrane  presents 

*  The  superposition  of  a  layer  of  nerve  cells  upon  a  layer  of  nerve 
fibres  recalls  the  structure  of  the  convolutions  of  the  cerebrum  and  cere- 
bellum. The  capillary  layer  of  the  retina  formed  by  the  branches  of  the 
arteria  centralis  retinae  occupies  the  stratum  of  nerve  cells.—  (Ed.)  j 


178  OKGAtfS    OF   SENSE. 

\ 

a  series  of  distinct  strata,  which,  proceeding  from 
without  inwards,  are  as  follows  :  1st,  the  membrana 
Jacobi,  composed  of  club-shaped  bodies;  2d,  the 
external  granular  layer,  corresponding  with  the  exter- 
nal enlargements  upon  the  fibres  of  Muller ;  3d,  the 
internal  granular  layer,  corresponding  to  the  middle 
enlargements  of  the  same  fibres ;  4th,  the  nervous 
layer,  consisting  of  nerve  cells;  5th,  the  fibrous 
layer  formed  by  the  fibres  of  the  optic  nerve ;  6th, 
and  last,  the  limitary  membrane.* 
Arteria  centraiis  The  central  artery  of  the  retina  traverses  the 

retinae.  * 

papilla  of  the  optic  nerve,  and  is  distributed  in  the 
more  internal  layers  of  the  retina.  It  forms  a  vas- 
cular circle  around  the  "  yellow  spot,"  and  terminates, 
by  a  second  circular  plexus,  at  the  ora  serrata.  The 
vein  has  the  same  distribution  as  the  artery. 
vitreous  ha-  Interior  of  the  eye. —  Vitreous  humor. — The  vitre- 
ous humor  of  the  eye  occupies  the  cavity  of  the 
retina,  and  is  adherent  to  that  membrane  only  in 
the  interval  between  the  ora  serrata  and  its  anterior 
margin  ;  in  front  it  presents  a  cup-shaped  depression 
which  receives  the  crystalline  lens.  Its  envelope,  the 
hyaloid  membrane,  is  very  delicate,  structureless,  and 
transparent;  interiorly  it  is  somewhat  thicker  than 
elsewhere,  and  gives  off  two  laminae,  which  invest, 
respectively,  the  anterior  and  posterior  surfaces  of 

*  To  obviate  any  obscurity  in  the  text,  arising  from  the  very  compen- 
dious and  precise  style  of  the  author,  who  always  assumes  that  his  reader 
is  a  good  descriptive  anatomist  and  possesses  alfair  knowledge  of  general 
structure,  it  would  be  well  for  the  student  to  refer  to  the  admirable  work 
of  TODD  and  BOWMAN,  "  The  Physiological  Anatomy  and  Physiology  of 
Man,'"1  where  fuller  details,  up  to  the  period  of  its  publication,  will  be 
found.  Vide  Vol.  IT.,  p.  27.  London,  1856.— 


mor. 


OEGANS    OF   SENSE.  1*79 

the  crystalline  lens,  enclosing,  at  their  angle  of  sepa- 
ration, the  canal  of  Petit,  which  surrounds  the  peri- 
pheral border  of  the  lens.  The  vitreous  humor, 
which  is  adherent  to  the  internal  face  of  this  mem- 
brane, is  an  amorphous  hyaline  substance  which,  in 
the  fo3tus,  contains  oxal  nuclei  and  stellate  cells ;  but 
in  the  adult  these  cellular  elements  are  no  longer 
visible,  and  nothing  remains  beyond  an  amorphous 
jelly-like  mass. 

The  vitreous  humor  contains  neither  nerves  nor 
vessels.  During  foetal  life  its  antero-posterior  axis  is 
occupied  by  a  tubular  canal,  containing  a  delicate 
branch  of  the  arteria  centralis  retinae  sent  forward  to 
the  capsule  of  the  lens ;  after  birth  this  canal  becomes 
obliterated. 

The  crystalline  lens  is  a  solid  body,  surrounded  by  crystalline  ie 
a  membranous  envelope.  This  containing  membrane, 
or  capsule,  of  the  lens  is  highly  transparent  and 
entirely  destitute  of  structure,  resembling  a  delicate 
lamina  of  the  purest  glass.  It  possesses  great  elasti- 
city, but  is  readily  torn ;  on  the  anterior  surface  of 
the  lens  its  thickness  is  ri  <rth  of  a  line,  and  posteriorly 
but  T loth  of  a  line.  It  resists  perfectly  the  action  of 
boiling  water,  a  solution  of  potassa,  and  the  acids. 
Its  external  surface  is  continuous  posteriorly  with  the 
hyaloid  membrane  of  the  vitreous  humor  ;  anteriorly 
it  is  free ;  its  internal  surface  is  lined  by  a  layer  of 
exceedingly  delicate  polygonal  cells,  which,  liquefy- 
ing shortly  after  death,  form  the  liquid  of  Morgagni.* 

*  John  Baptist  Morgagni,  the  celebrated  professor  of  anatomy  at  the 
University  of  Bologna  in  Italy,  and  the  preceptor  of  Scarpa,  was  born  in 
1682,  and  died  in  1771.— (Ed.) 


180  OEGANS    OF   SENSE. 

This  liquid  has  been  supposed  by  "some2  to  be  derived 
from  a  different  source,  viz.  from  a  layer  of  globules 
underlying  the  capsular  epithelium,  and  distinguish- 
able from  it  by  their  spherical  shape,  and  by  the 
absence  of  nuclei  in  their  contents  (Warlomont).* 

Beneath  the  epithelium  of  -the  capsule,  and  the 
globules  of  Morgagni,  is  the  proper  substance  of  the 
crystalline  lens,  which  consists  of  a  central  portion  or 
nucleus,  and  a  peripheral  or  cortical  portion.  The 
central  nucleus  is  a  little  star-shaped  mass,  made  up 
entirely  of  very  minute  granules.  The  cortical  por- 
tion of  the  lens  is  composed  of  concentric  lamellae, 
and  each  lamella,  of  hexagonal  prisms  in  close  appo- 
sition and  flattened  antero-posteriorly.  These  pris- 
matic bodies  are  more  numerous  and  delicate  in  their 
proportions  as  we  trace  them  more  deeply  into  the 
substance  of  the  lens,  and  they  adhere  to  each  other 
more  closely  by  their  edges  than  by  their  faces,  which 
explains,  on  one  hand,  why  the  substance  of  the  lens 
increases  in  density  from  its  surface  towards  its  cen- 
tre, and  on  the  other,  why  it  disintegrates  more 
readily  into  laminae  than  into  fibres.  They  consist 
of  a  very  delicate  and  structureless  containing  mem- 
brane, with  contents  of  a  semi-fluid  consistence, 
equally  destitute  of  structure,  and  albuminous  in 
their  nature ;  their  edges  are  serrated,  and  the  inter- 
digitation  of  these  serrations  adds  to  the  solidity  of 
their  union. 

Each  prism,  taking  its  origin  from  one  of  the  pro- 
longations of  the  central  nucleus  of  the 'lens,  passes 

*  Dr.  E.  Warlomont,  chief  editor  of  the  *  Annales  d'Oculistique,'  pub- 
lished at  Brussels,  Belgium.— (Ed.} 


ORGANS    OF    SENSE.  181 

outwards  towards  its  border  wliicli  it  doubles,  and 
returns  upon  its  opposite  surface,  where  it  terminates ; 
its  two  faces  do  not  give  the  same  measurement  in 
length,  which  is  explained  by  the  fact  that  its  extre- 
mities are  both  beveled,  and  in  opposite  directions. 

Neither  the  crystalline  lens  nor  its  capsule  possesses 
vessels  or  nerves,  at  least  in  the"  adult.  During  foetal 
life,  the  branch  of  the  central  artery  of  the  retina, 
which  traverses  the  tubular  canal  in  the  vitreous 
humor,  furnishes  branches  which  encircle  the  capsule, 
and  afterwards  lose  themselves  in  the  pupillary  mem- 
brane, where  they  anastomose  with  the^ciliary  arte- 
ries. 

The  histological  development  of  the  eye  follows  Development. 
the  universal  law;  all  of  its  component  parts  take 
their  origin  from  embryonic  cells  which  take  on 
determinate  metamorphoses  in  order  to  form  each  of 
its  individual  tissues.  Each  of  the  prismatic  fibres  of 
the  crystalline  lens  is  the  result,  apparently,  of  the 
.elongation  of  a  single  cell,  and  not  of  the  fusion 
together  of  an  indefinite  number  of  cells. 

SECT.  II.  THE  EAE. — The  skeleton  of  the  external  External  ear. 
ear  is  osseous  in  the  deep  portion  of  the  meatus,  but 
elsewhere  it  is  fibro-cartilaginous.  The  integument 
by  which  it  is  invested  contains  glands  of  different 
kinds  in  its  several  regions.  In  the  concha  we  find 
a  great  many  sebaceous  glands ;  we  encounter  these 
organs  again  in  the  external  meatus,  but  here  they 
are  in  company  with  ceruminous  glands ;  finally, 
sudoriparous  glands  are  found  everywhere,  but  prin- 
cipally upon  the  internal  surface  of  the  concha. 

There  is  nothing  especially  worthy  of  notice  in  the 


182  OKGANS    OF   SENSE. 

mode  of  distribution  of  the  vessels  and  nerves  of  the 
external  ear. 

Middle  ear.  The  mucous  membrane  of  the  middle  ear  is  very 
thin ;  in  the  Eustachian  tube  only  it  is  somewhat 
thicker.  From  the  bony  walls  of  the  cavity  it  is 
reflected  upon  the  inner  surface  of  the  membrana 
tympani  to  which  it  is  closely  adherent,  and  upon 
the  muscles  and  ossicula,  for  which  it  forms  a  perios- 
teal  investment.  Its  epithelium  is  everywhere  cili- 
ated, except  upon  the  internal  surface  of  the  mem- 
l)rana  tympani,  where,  according  to  Kolliker,  it'  forms 
a  simple  tessellated  layer. 

The  membrana  tympani  consists  of  a  fibrous  ex- 
pansion made  up  of  radiating  and  circular  fasciculi, 
and  inserted  by  its  circumference  into  the  groove  of 
the  temporal  bone  like  a  watch  crystal  into  its  case  ; 
we  are  familiar  with  the  relation  of  its  internal  sur- 
face to  the  mucous  lining  of  the  tympanum  ;  its  ex- 
ternal surface  receives  a  layer  of  epidermis  from  the 
walls  of  the  meatus  auditorius  externus. 

The  blood-vessels  of  the  middle  ear  are  numerous ; 
they  form  a  rich  network  in  the  substance  of  its  mu- 
cous membrane,  and  in  the  membrana  tympani.  The 
lymphatic  vessels  probably  accompany  its  arteries 
and  veins. 

The  nerves  of  the  middle  ear  come  from  the  fifth, 
seventh,  and  ninth*  pairs  of  cranial  nerves;  their 
mode  of  termination  is  unknown  ;  Kolliker  describes 
masses  of  ganglionic  cells  as  existing  in  the  substance 
of  the  tympanic  nerve. 
internal  ear.  The  bony  walls  of  the  semicircular  canals,  vesti- 

*  According  to  the  classification  of  Scemmering. 


ORGANS    OF   SENSE.  183 

bula,  and  cochlea,  are  covered  by  a  layer  of  connect- 
ing tissue,  with  pavement  epithelium  upon  its  surface. 

The  walls  of  the  membranous  labyrinth  consist  of 
a  lamina  of  extremely  delicate  connecting  tissue,  the 
fibrillated  character  of  which  is  with  difficulty  recog- 
nizable, but  it  contains  a  large  quantity  of  oval  (fibro- 
plastic)  nuclei,  and  is  covered  by  a  very  thin  amor- 
phous layer,  on  the  internal  surface  of  which  we  find 
a  stratum  of  pavement  epithelium. 

The  white  specks  which  are  observed  upon  the 
inner  surfaces  of  the  sacculus  communis  and  sacculus 
proprius  (otoliths,  otoconites)  are  composed  of  cal- 
careous granules,  which  sometimes  present  a  crystal- 
line aspect.  Both  outside  and  inside  of  the  tubes 
and  cavities  forming  the  membranous  labyrinth,  is  a 
pellucid  fluid  (pe.rilymph,  endolymph),  the  chemical 
nature  of  which  is  not  as  yet  clearly  determined. 

The  nerves  which  reach  the  ampullae  of  the  semi- 
circular canals  and  the  sacculi  appear  to  terminate 
by  free  extremities,  after  having  undergone  frequent 
division  and  subdivision ;  beyond  these  localities  it 
has  been  found  impossible  to  trace  them. 

The  vessels  form  a  close  network  which  principally 
occupies  the  fibrous  coat  of  the  semicircular  canals, 
and  the  two  vestibular  sacculi. 

The  labors  of  Corti*  and  Kolliker  tend  to  prove 
that  the  nervous  fibres  of  the  cochlea  terminate  by 
free  extremities  in  the  substance  of  the  membranous 
portion  of  the  lamina  spiralis.  These  authors  have 
also  demonstrated  that  there  are  cellular  enlarge- 

*  Corti  wrote  on  the  structure  of  the  retina  in  Miiller's  Archiv,  1850, 
p.  274.— (Ed.} 


184  ORGANS    OF   SENSE. 

ments  in  the  course  of  these  fibres,  analogous  to  those 
of  the  nerve  fibres  of  the  retina. 

The  capillary  network  formed  by  the  blood-vessels 
of  the  cochlea  is  equally  rich  with  that  of  the  vesti- 
bule and  semicircular  canals. 

SECT.  III.  OLFACTORY  Mucous  MEMBRANE. — The 
mucous  lining  of  the  nasal  cavities  is  thick,  soft, 
tomentose,  and  reddish  in  color,  especially  in  its  in- 
ferior two-thirds.  Its  texture  is  composed  of  inter- 
woven fibres — connective  and  elastic — but  the  pro- 
portion of  the  latter  is  small ;  it  contains  likewise 
an  abundance  of  plasmatic  cells.  Its  deeper  surface  is 
intimately  adherent  to  the  periosteum,  and  contains 
a  great  number  of  mucous  follicles,  in  clusters.  Its 
free  surface  is  covered  by  stratified  epithelium,  and 
its  superficial  layer  of  conical  cells  is  provided  with 
cilia.  Its  vessels  are  exceedingly  numerous,  and  form 
a  web  of  unusual  thickness.  The  nervous  filaments 
furnished  by  the  fifth  pair  are  distributed  throughout 
its  whole  extent,  and  present  nothing  worthy  of  note, 
but  those  which  come  from  the  olfactory  nerve  are 
distributed  only  to  the  mucous  membrane  covering 
the  superior  turbinated  bone,  and  the  upper  third  of 
the  septum  between  the  nostrils;  moreover,  they 
apparently  end  by  free  extremities.  According  to 
some  authors  they  present  globular  enlargements  at 
their  extremities,  similar  to  those  of  the  retina. 

THE   END. 


EXPLANATION  OF  THE  PLATES. 


PLATE  I. 

VARIOUS   FORMS    OF   CELLS. 

FIG.  L*  Blood  of  the  adult. — 1,  Red  globules,  front  view; 
2,  same  in  profile ;  3,  same  altered  ;  4,  white  globule. 

FIG.  II.  Epithelial  cells  of  the  bladder.— 1,  Cell  with 
granular  contents ;  2,  its  nucleus,  also  containing  granules,  one 
of  which  (3)  larger  than  the  rest  forms  the  nucleolus ;  4,  cell 
with  two  nuclei ;  5,  group  of  cells  retaining  their  original  rela- 
tion to  each  other. 

FIG.  III.  Hepatic  cells. — They  are  polygonal  in  shape,  and 
scattered  amongst  their  granular  contents  free  fat  is  to  be  seen 
in  the  form  of  brilliant  little  pearl-like  globules. 

FIG.  IV.  Epidermic  cells. — 1,  Cells  of  the  rete  mucosum  / 
2,  cells  of  the  middle  stratum ;  3,  cells  of  the  surface,  in  the 
shape  of  granular  scales  without  nuclei ;  4,  other  cells  from  the 
superficial  layer,  detached  and  swelled  by  very  dilute  acid. 

FIG.  V.  Adipose  cells  from  beneath  the  integument.  Their 
fluid  contents  are  so  transparent  that  the  outlines  of  the. cells 
alone  are  visible. 

!      *  "(i't  •  ••'     ':    •'  •'•     '  •' '  •  Fil'J-J  ii-'».  >'•!/<"' iI>'G 

FIG.  VI.  Epithelial  cells  from  the  small  intestine,  exa- 
mined thirty  hours  after  death. 

FIG.  VII.  Epithelial  cells  of  the  trachea.— 1,  Body  of 

*  All  of  the  figures  contained  in  the  following  plates,  unless  otherwise 
stated,  were  drawn  from  preparations  taken  from  the  adult  male  subject, 
and  magnified  400  diameters  by  a  Nachet's  microscope. 

12 


186         EXPLANATION  OF  THE  PLATES. 

a  ciliated  cell  with  its  nucleus ;  2,  outline  of  the  layer  of  amor- 
phous material  at  its  base ;  3,  cilia ;  4,  deeper  cells  of  the  same 
layer  ;  5,  normal  relation  of  these  cells.  The  ciliated  cells  con- 
stitute the  free  surface  of  the  epithelial  membrane. 


PLATE  H. 

CELLS,  continued;  CONNECTING  TISSUE. 

FIG.  I.  Pigment  cells  from  the  deep  surface  of  the  choroid. 
They  are  very  regular  polygons  filled  with  granules  of  pigment, 

except  in  the  centre,  where  the  bright  spot  corresponds  with 

••  .1  .•:;.-: 
the  nucleus. 

FIG.  II.  Branching  pigment  cells  from  the  outer  surface 
of  the  choroid;  1,  cell;  2,  nucleus;  3,  anastomosing  branch; 
4,  nucleus  of  oval  or  fusiform  cells,  scattered  amongst  very  pale 
connective  fibres. 

FIG.  III.   Fusiform  cells  (fibro-plastic). 

FIG.  IV.  Adipose  cells  containing  acicular  crystals  of  mar- 
garine in  tufts,  or  solitary. 

FIG.  V.  Plasmatic  cells,  or  nuclei  of  the  cornea.  Their 
anastomoses  are  perceptible. 

FIG.  VI.  Cells  from  a  cancer  of  the  heart,  in  which  endo- 
genous multiplication  of  the  nuclei,  by  cleavage,  is  seen. 

FIG.  VII.  Another  type  of  cancer  cell,  showing  process 
of  endogenous  multiplication  of  nuclei  by  cleavage. — 1,  Nucleus 
in  process  of  cleavage  ;  2,  separate  nuclei. 

FIG.  VIII.  Multiplication  of  cells. — 1,  Process  of  endo- 
genous formation  as  observed  in  fo3tal  marrow ;  2,  multiplica- 
tion by  cleavage  in  the  cartilage  cell. 

FIG.  IX.  Superficial  fascia  of  the  forearm.  It  is  com- 
posed of  fasciculi  of  connective  fibres  :  1,  wavy  and  crossing  in 
all  directions  so  as  to  form  an  interlacement  varying  in  density. 
Amongst  these  fasciculi  a  number  of  elastic  fibres  (2)  are  to  be 
seen. 


EXPLANATION    OF   THE   PLATES. 

PLATE  HI. 

CONNECTING  TISSUE,  continued. 

FIG.  I.  Connective  fibres  in  wavy  and  parallel  bundles. 
On  the  right  of  the  preparation  they  have  been  slightly  teased 
out  (tendo  Achillis). 

FIG.  II.  Longitudinal  section  of  tendon  (tendo  Achillis), 
treated  by  acetic  acid.  The  fasciculi  of  connective  fibres  have 
grown  pale  and  disappeared.  1,  Plasmatic  cells  in  longitudinal 
rows  between  the  fasciculi  of  fibres ;  2,  anastomoses  between 
them  (from  the  fetus). 

FIG.  III.  Longitudinal  section  of  tendon  (Peronceus 
longus). — 1,  Bundles  of  connective  fibres  ;  2,  plasmatic  cells. 

FIG.  IV.  Transverse  section  of  the  tendon  of  the 
Peronseus  longus. — 1,  Granular  basis  indicating  the  section  of 
the  connective  fibres;  2,  irregular  wavy  lines  marking  the 
intervals  between  the  fasciculi ;  3,  plasmatic  cells. 

FIG.  V.  Elastic  fibres  from  a  yellow  ligament. — 1,  The 
fibres  in  their  normal  relation  ;  2,  separate  fibres. 


PLATE  IV. 

CONNECTING  TISSUE,  continued. 

FIG.  I.  Longitudinal  section  of  the  superior  extremity 
of  the  tendo  Achillis  (of  an  old  man). — 1,  Fasciculus  of  con- 
nective fibres ;  2,  plasmatic  cells  in  parallel  rows. 

FIG.  II.  Similar  section  of  inferior  extremity  of  same 
tendon.  1,  Connective  fibres,  slightly  wavy ;  2,  cartilage  cells 
which  have  taken  their  origin  from  plasmatic  cells. 

The  following  figures  show  the  different  modes  of  develop- 
ment of  connective  fibres. 

FIG.  III. — 1,  Embryonic  cell;  2,  same  cell  elongated,  its 
contents  already  divided  into  fibrilla? ;  3,  two  cells  united  at 
their  extremities,  about  to  form  a  bundle  of  connective  fibres. 


188        EXPLANATION  OF  THE  PLATES. 

FIG.  IV.  Fibrous  tumor  of  the  dura-mater. — 1,  Free 
fusiform  cells ;  2,  fasciculi  of  same  cells  united  at  their  extremi- 
ties ;  3,  fasciculi  of  fibres  formed  by  the  elongation  of  the  same 
cells  and  the  disappearance  of  their  nuclei.  In  this  case  each 
row  of  cells  forms  but  one  solitary  fibre. 

FIG.  V.  Fibrous  tumor  of  the  uterus  in  which  the  for- 
mation of  a  fibre  by  metamorphosis  of  a  nucleus  can  be  traced. 
1,  Finely  granular  substance  ;  2,  nuclei. 

FIG.  YI.  Another  portion  of  same  tumor.  The  nuclei 
somewhat  elongated  in  shape  already  show  a  disposition  to 
assume  the  form  of  fibres. 

FIG.  VII.  Same  tumor.  The  nuclei  are  still  more  elon- 
gated ;  at  some  points  they  can  be  seen  with  their  extremities 
united  together  so  as  to  form  fibres. 


PLATE   V. 

CAETILAGE  AND   BONE. 

FIG.  I.  Section  involving  the  centre  of  a  costal  carti- 
lage. 1,  Fundamental  substance,  slightly  granular  and  trans- 
parent ;  2,  cartilaginous  capsule ;  3,  primordial  cell,  or  utricu- 
lus ;  4,  nucleus — made  up  of  fatty  granules  ;  5,  capsule  contain- 
ing four  cells,  two  of  which  have  no  nuclei. 

FIG.  II.  Costal  cartilage  with  its  perichondrium,  taken 
from  a  subject  eighteen  years  of  age.  1,  Perichondrium  formed 
by  a  dense  interlacement  of  connective  and  elastic  fibres,  and 
studded  with  plasmatic  cells.  2,  There  is  no  clear  and  distinct 
line  of  demarcation  between  the  deepest  portion  of  the  peri- 
chondrium and  the  substance  of  the  cartilage ;  it  is  also  almost 
impossible  to  make  out  a  distinct  difference  in  the  character  of 
the  superficial  cells  of  the  cartilage  and  the  plasmatic  cells  of 
the  deepest  layer  of  the  perichondrium. 

FIG.  III.  Fibro-cartilage  from  the  ear.  1,  Fibrous  fun- 
damental substance  or  basis ;  2,  capsule  inclosing  these  cells. 

FIG.  IV.  Transverse  section  of  the  ulna.    In  the  midst 


EXPLANATION    OF   THE    PLATES.  189 

of  the  amorphous  fundamental  substance  of  the  line  are  to  be 
seen:  1,  the  stellate  or  branching  bone-cells  (lacunae);  their 
branches  or  prolongations  (2)  in  the  shape  of  canaliculi,  anasto- 
mosing with  each  other  so  as  to  form  a  network  by  which  a 
communication  is  established  between  the  corpuscles  themselves, 
and  also  with  the  Haversian  canals  3,  or  with  the  interior  cavi- 
ties of  the  bone. 

FIG.  V.  Same  section  seen  with  a  magnifying  power  of 
eighty  diameters.  The  bone-corpuscles  (lacunae),  in  the  shape 
of  minute  elongated  black  spots,  are  seen  to  be  grouped  in  con- 
centric circles  around  the  Haversian  canals  (1). 


,'  rl   ;  (L'o 


PLATE  VI. 

BONE,  continued. 


FIG.  I.  Longitudinal  section  of  the  shaft  of  the  femur 

(80  diameters).  1,  Longitudinal  Haversian  canals;  2,  trans- 
verse anastomotic  canal ;  3,  confluence  of  several  canals. 

FIG.  II.  Longitudinal  section  of  the  condyles  of  the 
femur  (in  a  newly  born  infant.  Magnifying  power  of  180 
diameters).  1,  Line  of  junction  of  the  cartilage  with  the  bone. 
Above  this  line  the  cells  of  the  cartilage  are  seen  grouped  in 
parallel  rows.  Their  nuclei  (2)  deeply  shaded  and  presenting 
jagged  edges.  Below  this  same  line  the  cartilage  is  seen,  infil- 
trated with  earthy  salts  and  in  process  of  ossification. 

FIG.  III.  Section  of  cartilage  taken  from  same  femur  y^th 
of  an  inch  beyond  the  newly  ossified  portion.  1,  Fundamental 
substance,  entirely  transparent ;  2,  limit  of  the  capsule ;  3,  limit 
of  the  cell ;  4,  nucleus  assuming  a  branching  character. 

FIG.  IV.  Formation  of  marrow  and  of  medullary  cavi- 
ties in  newly  ossified  bone  (from  same  femur).  1,  Fundamen- 
tal substance  infiltrated  at  certain  points  with  free  fat  2  ;  3, 
capsule  of  cartilage  cells ;  4,  a  parent  cell  full  of  young  cells ; 
5,  unbroken  partition  between  two  capsules ;  6,  cavity  resulting 
from  the  fusion  of  several  cells ;  it  contains  young  cells  (cells  of 


190  EXPLANATION    OF   THE   PLATES. 

foetal  marrow)  and  a  great  deal  of  free  fat ;  7,  angle  correspond- 
ing to  position  of  a  partition  which  has  disappeared. 

FIG.  V.  Ossification  "by  periosteum  (femur  of  a. newly 
born  infant).  1,  Completely  formed  bone;  2,  deepest  portion 
of  the  periosteum,  in  which  some  connective  fibres  and  a  large 
number  of  plasmatic  cells  can  be  still  distinguished  ;  of  the  lat- 
ter, those  nearest  the  bone  begin  to  resemble  bone  corpuscles 
in  shape ;  3,  superficial  portion  of  periosteum,  show  few  plas- 
matic cells  and  numerous  connective  fibres ;  4,  plasmatic  cells. 


PLATE  VII. 
BONE,  continued ;  TEETH. 

FIG.  I.  Ossification  of  the  os  frontis  at  the  margin  of  the 
anterior  fontanelle  (from  an  infant  four  months  old)  ;  1,  recently 
formed  bone ;  2,  deepest  portion  of  the  periosteum ;  3,  super- 
ficial portion  of  the  periosteum.  The  plasmatic  cells,  in  this 
specimen,  give  off  distinctly  marked  branches. 

FIG.  II.  Ossification  of  cartilage,  according  to  the  most 
generally  received  theory. — 1,  Capsule  and  cells,  unaltered; 
first  appearance  of  the  corrugation  of  the  cell-wall ;  3,  corru- 
gation more  marked  ;  4  and  5,  corrugation  still  farther  advanced 
and  completed,  resulting  in  formation  of  a  bone-corpuscle. 

FIG.  III.  Transverse  section  of  the  canalieuli  of  the 
ivory  of  a  tooth. — 1,  Canalieuli;  2,  their  anastoniotic 
branches  ;  3,  canaliculi  divided  a  little  obliquely. 


PLATE  VIII. 

TEETH,  continued. 

FIG.  I.  Incisor  tooth  of  a  child  nine  years  old — magnified 
thirteen  diameters. — 1,  Dental  cavity  ;  2,  ivory ;  3,  cementum 
investing  its  root ;  4,  enamel  covering  its  crown. 


EXPLANATION    OF   THE   PLATES.  191 

FIG.  II.  Ivory  and  cementum. — 1,  Amorphous  substance ; 
canaliculi  of  the  ivory,  with  their  lateral  anastomotic  branches ; 
3,  dilatations  in  the  course  of  the  canaliculi ;  4,  confluence  of 
several  canaliculi ;  5,  inter-globular  spaces ;  6,  cementum  with 
very  large  bone-corpuscles.  Some  of  these  latter  communicate 
with  the  cavities  of  the  inter-globular  spaces. 

FIG.  III.  Transverse  section  of  the  crown  of  a  large 
molar  tooth. — 1,  Ivory,  and  terminations  of  its  canaliculi ;  some 
of  these  canaliculi  enlarge  in  diameter  (2)  and  penetrate  the 
substance  of  the  enamel ;  3,  enamel,  consisting  of  wavy  and 
parallel  prisms  ;  they  are  seen  in  groups  slightly  diverging  from 
each  other  ;  4,  lines  of  separation  between  the  prisms. 

FIG.  IV.  Transverse  section  of  enamel. — 1,  Prisms  seen 
in  transverse  section  ;  prisms  divided  a  little  obliquely.  The 
white  lines  are  the  intervals  between  the  prisms. 


PLATE  IX. 

MUSCLE. 

FIG.  I.  Muscular  coat  of  the  stomach  treated  by  acetic 
acid. — 1,  Finely  granulated  muscular  fibre,  with  very  pale  out- 
lines, often  indistinctly  visible  ;  2,  nuclei ;  3,  lines  of  separation 
between  the  muscular  fibres  ;  4,  elastic  fibres. 

FIG.  II.  Same  coat  in  transverse  section,  and  hardened  by 
moderate  boiling. — 1,  Muscular  fibres;  2,  nuclei;  3,  line  of 
separation  between  the  fibres;  4,  outline  of  a  fasciculus  of  mus- 
cular fibres. 

FIG.  III.  Dartos  treated  by  acetic  acid. — 1,  Very  pale  finely 
granulated  substance,  corresponding  to  the  muscular  fibres  ;  2, 
elongated  nuclei. 

FIG.  IV.  Embryonic  fibres  of  striped  muscle. — 1,  Two 
varicose  fibres  formed  by  the  union  of  embryonic  cells;  2, 
nuclei  of  these  cells  ;  3,  two  other  fibres,  a  little  longer  and  less 
varicose ;  4,  division  of  the  contents  of  the  cells  into  granules 
and  transverse  striae ;  5,  fibres  showing  the  commencement  of 


192  EXPLANATION    OF   THE   PLATES. 

striation  in  the  direction  of  their  length ;  6,  another  fibre,  in 
which  this  appearance  is  more  strongly  marked. 

FIG.  V.  G-emellus  muscle  hardened  by  cooking  (from  a 
newly  born  infant). — 1,  Myolemma ;  2,  its  contents,  showing 
transverse  striae  ;  3,  nucleus ;  4,  a  broken  fibre,  with  its  con- 
tents divided  into  discs ;  5,  a  fibre  in  which  the  division  of  its 
contents  into  discs  is  very  well  marked. 


PLATE  X. 

MUSCLE,  continued. 

FIG.  I.  Antero-posterior  section  of  the  tongue  (in  a 

newly-born  infant). — 1,  Muscular  fasciculi  seen  in  the  direction 
of  their  length;  2,  same,  in  transverse  section. 

FIG.  II.  Different  views  of  striped  muscular  fibre. — 
1,  A  fibre,  the  contents  of  which  are  crushed  in  two  places ;  at 
its  left  extremity  its  myolemma  is  very  well  seen,  corrugated 
and  contracted  upon  itself;  2,  a  fibre  with  transverse  striae, 
showing  a  nucleus  (3)  ;  4,  a  fibre  in  which  both  longitudinal 
and  transverse  stripes  are  visible ;  5,  another  fibre  broken  off  at 
its  upper  -extremity ;  each  fib  rill  a  is  seen  to  be  composed  of  a 
series  of  slightly  flattened  granules  superimposed  upon  each 
other.  All  of  these  muscular  fibres  were  procured  from  the 
perfectly  fresh  biceps  muscle  of  a  suicide. 

FIG.  III.  Fibres  of  the  heart. — 1,  A  common  trunk  giving 
off  several  brandies  ;  2,  divisions  of  the  trunk. 


PLATE  XI. 

Distribution  of  the  nerves  as  seen  in  the  subcutaneous  pec- 
toral muscle  of  a  frog.  The  parallel  lines  indicate  the  outlines 
of  the  muscular  fibres. 


EXPLANATION    OF   THE    PLATES.  193 


PLATE  XII. 

ELEMENTS    OP   NERVE   TISSUE. 

FIG.  I.  Nerve  fibres. — 1,  Nerve  fibres  of  the  large  variety  ; 
2,  envelope  of  the  fibres ;  3,  its  contents ;  4,  another  fibre 
treated  by  chromic  acid ;  5,  envelope ;  6,  medulla ;  7,  axis 
cylinder ;  8,  fine  nerve  fibres  with  a  single  outline,  taken  from 
the  spinal  marrow. 

FIG.  H.  Fibres  of  Remak  taken  from  a  sympathetic  gan: 
glion  from  the  lumbar  region. 

FIG.  III.  and  IV.  Connexion  between  nerve-fibres  and 
ganglionic  cells  (after  Leydig). 

FIG.  Y.  Connexion  between  nerve-fibres  and  cells  of 
the  spinal  marrow.  1,  Central  canal  of  the  medulla  spinalis ; 
2,  nerve-cells ;  3,  superior  prolongation ;  4,  inferior  prolonga- 
tion ;  5,  anterior  root ;  6,  posterior  root ;  7,  transverse  pro- 
longation forming  the  anterior  commissure  and  establishing  anas- 
tomoses between  the  cells  of  the  two  halves  of  the  spinal  mar- 
row (after  Owsjauikow). 

FIG.  VI.  Nerve-cells. — 1,  Cells  with  one  prolongation 
(unipolar)  from  a  dorsal  ganglion  of  the  sympathetic ;  2,  ano- 
ther cell  from  the  ganglion  of  Gasser  (on  the  fifth  cranial 
nerve) ;  3,  mass  of  pigment. 


PLATE  XIII. 

ELEMENTS    OF   NERVE   TISSUE. 

FIG.  I.  Nerve  cells. — 1,  Simple  (apolar)  cells  from  the  grey 
matter  of  the  brain ;  2,  multipolar  cells  from  the  grey  matter 
of  the  cerebellum  ;  3,  cell  from  the  floor  of  the  fourth  ventricle ; 
4,  another  cell  from  the  grey  matter  of  the  cord  in  the  cervical 
region;  5,  nucleus;  6,  mass  of  pigment  surrounding  the 
nucleus ;  7,  two  cells  from  the  ganglion  of  Gasser  ;  one  of  them 
has  a  nucleated  envelope  (8). 


194  EXPLANATION    OF   THE    PLATES. 

FIG.  II.  Grey  matter  from  the  cerebellum.— 1,  Apolar 
cells  ;  2,  mass  of  nuclei  grouped  around  the  cells  ;  3,  fine  nerve 
fibres — varicose. 

FIG.  III.  Superior  cervical  ganglion. — 1,  Nerve  cells 
imbedded  in  a  faintly  fibrillated  substance  containing  nuclei 
similar  to  those  represented  on  the  cell  at  (8). 


PLATE  XIY. 

TERMINATION    OF   NERVE-FIBKES. AKTEKIES. 

FIG.  L  Nerve-fibre  from  the  subcutaneous  pectoral  mus- 
cle of  the  frog ;  1,  muscular  fibre ;  2,  nerve  fibre;  3,  terminal 
ramifications. 

FIG.  II.  Pacinian  corpuscle. — 1,  Its  pedicle ;  2,  its  cor- 
tical substance  divided  into  lamellae  by  concentric  lines,  on  the 
concave  surface  of  which  numerous  little  nuclei  are  seen  pro- 
jecting ;  3,  its  central  cavity  filled  with  finely  granular  matter, 
and  a  considerable  number  of  nuclei  with  pale  outlines  ;  4,  the 
nerve  fibre  which  forms  the  axis  of  its  pedicle,  running  into  its 
central  cavity,  where  it  ends  in  a  slight  enlargement. 

FIG.  III.  Termination  of  a  nerve  fibre  of  the  retina 
(after  H.  Muller). — 1,  Nerve-cells ;  2,  fibres  from  the  optic 
nerve ;  3,  another  fibre  on  its  way  to  rejoin  the  club-shaped 
bodies  of  the  external  layer  of  the  retina. 

FIG.  IV.  Transverse  section  of  the  primitive  carotid 
artery  of  a  child  15  years  of  age — magnified  120  diameters. — 
1,  Internal  coat ;  2,  middle  coat ;  3,  external  coat. 

FIG.  V.  The  same  section  treated  by  acetic  acid  and  exa- 
mined with  a  magnifying  power  of  400  diameters. — 1,  Internal 
coat ;  the  transverse  section  of  the  elastic  fibres  of  which  it  is 
composed  are  visible ;  2,  middle  coat ;  3,  nuclei  of  muscular 
fibres ;  there  is  a  pale  line  (4)  on  each  side  of  the  nuclei,  indi- 
cating the  limits  of  the  muscular  fibres ;  5,  elastic  fibres ;  6, 
same,  in  transverse  section. 

FIG.  VI.  The  same  artery. — 1,  Middle  coat ;  2,  external 
coat,  composed  of  elastic  fibres,  most  of  which  run  longitudi- 


EXPLANATION    OF   THE   PLATES.  195 

nally,  and  which  are  more  numerous  and  closer  together  towards 
its  internal  limit.  Between  these  elastic  fibres  are  connective 
fibres  which  grow  pale  and  break  down  under  the  action  of 
acetic  acid,  leaving  a  hyaline  mass  (3). 

FIG.  VII.  Middle  coat  of  a  branch  of  the  artery  occupying 
the  fissure  of  Sylvius ;  it  is  composed  entirely  of  muscular  fibres, 
no  traces  of  elastic  fibres  being  visible. 

FIG.  VIII.  Four  muscular  fibres  from  the  basilar  artery. 
The  two  on  the  right  have  been  subjected  to  the  action  of  acetic 
acid,  by  which  they  are  rendered  pale,  and  their  nuclei  much 
more  distinct. 


PLATE  XV. 

ARTERIES,  continued. 

FIG.  I.  Epithelial  layer  of  the  internal  coat  (from  the 
radial  artery). — 1,  Nucleus  ;  2,  internuclear  substance  composed 
of  cells  the  outlines  of  which  are  not  visible. 

FIG.  II.   Epithelial  cells,  isolated  (from  the  radial  artery). 

FIG.  III.  Fenestrated  layer. — 1,  Amorphous  material 
through  which  the  fibres  of  the  subjacent  coat  are  visible ;  2, 
elastic  fibres  imbedded  in  the  amorphous  substance  ;  3,  openings 
or  fenestra,  of  various  shapes  and  sizes ;  4,  irregular  line  show- 
ing where  the  layer  has  torn  or  ruptured  ;  5,  the  subjacent  layer 
consisting  of  longitudinal  elastic  fibres  (from  the  radial  artery). 

FIG.  IV.  Longitudinal  section  of  the  primitive  carotid 
artery  of  a  young  subject  (15  years  of  age)  ;  1-2,  internal 
coat ;  2-3,  middle  coat ;  4,  muscular  fibres  of  the  middle  coat ; 
5,  their  nuclei ;  6,  network  of  elastic  fibres ;  7,  transverse  sec- 
tion of  these  same  fibres. 

FIG.  V.  Same  artery,  dried  like  the  preceding,  and 
treated  by  acetic  acid. — 1,  Line  of  junction  of  its  middle  and 
external  coats.  The  latter  (2)  consists  of  a  web  of  elastic  fibres, 
which  run  mostly  parallel  with  the  axis  of  the  vessel,  and  are 
crossed  by  connective  fibres ;  these  have  been  rendered  invisible 
by  the  acetic  acid. 


196   ^     EXPLANATION  OF  THE  PLATES. 

FIG.  VI.  A  recent  specimen  of  the  external  coat  of  an 
artery  simply  spread  out  upon  the  glass. — 1,  Elastic  fibres  ;  2, 
fasciculi  of  connective  fibres. 

FIG.  VII.  A  small  artery  of  the  brain,  measuring  J¥  th  Of 
a  line  in  diameter,  treated  by  very  dilute  acetic  acid. — 1,  Ex- 
ternal coat  consisting  of  connective  fibres ;  2,  transverse  mus- 
cular cells ;  3,  their  nuclei ;  they  form  the  middle  coat.  Beneath 
this,  oval  nuclei  can  be  distinguished  (4)  with  their  long  dia- 
meters in  the  direction  of  the  axis  of  the  vessel.  They  are 
imbedded  in  a  thin  layer  of  amorphous  substance,  and  constitute 
the  internal  coat. 

FIG.  VIII.  Two  capillaries  from  the  brain,  the  upper 
measuring  al^th  and  the  lower  2^otn  OI>  a  ^me  *n  diameter. — 
1,  Structureless  wall;  2,  nuclei  contained  in  the  thickness  of 
this  wall ;  3,  cavity  of  the  vessel. 


PLATE  XVI. 

VEINS. 

FIG.  I.  Capillary,  measuring  T£¥  of  a  line  in  diameter ;  2, 
minute  vein,  measuring  ¥£^th  ;  their  walls  are  formed  by  con- 
nective fibres  running  lengthwise  of  the  vessel  and  studded 
with  numerous  plasmatic  cells  (3). 

FIG.  II.  Transverse  section  of  the  femoral  vein — first 
dried  and  then  treated  by  acetie  acid. — 1-2,  Internal  coat;  2-3, 
middle  coat ;  3-4,  external  coat.  In  the  internal  coat  some  of 
the  elastic  fibres,  of  which  it  is  constituted,  are  seen  in  longi- 
tudinal, and  others  in  transverse  section  ;  5,  strata  of  muscular 
fibres  very  well  characterized  by  their  club-shaped  nuclei  (6), 
the  outlines  of  which  are  clear  and  distinct ;  7,  other  muscular 
fibres,  seen  in  transverse  section,  most  of  them  having  a  nucleus 
(8) ;  9,  strata  of  elastic  and  connective  fibres  alternating  with 
the  strata  of  muscular  fibres.  The  external  coat  is  similar  to 
that  of  the  arteries. 

FIG.  III.  Valve  from  the  internal  Saphoena  vein. — 


EXPLANATION   OF   THE   PLATES.  197 

1,  Epithelium ;  the  oval  nuclei  of  its  cells  only  are  visible,  the 
outlines  of  the  cells  themselves  being  too  pale ;  2,  subjacent 
layer,  formed  exclusively  of  regularly  undulating  connective 
fibres. 

FIG.  IV.  Elastic  sub-epithelial  membrane  from  a  small 
mesenteric  vein,  treated  by  acetic  acid. — 1,  Web  of  elastic  fibres ; 

2,  openings  of  different  dimensions,  giving  this  layer  the  same 
appearance  as  the  fenestrated  coat  of  an  artery ;  3,  nuclei  of  its 
muscular  coat,  seen  by  transmitted  light. 

FIG.  Y.  A  mesenteric  vein  of  yL-th  of  a  line  in  diameter. — 
1,  Its  external  coat,  made  up  of  elastic  fibres,  connective  fibres, 
and  plasmatic  cells  (2) ;  3,  middle  coat,  entirely  muscular ;  4, 
the  cells  which  form  its  muscular  fibres  in  transverse  section, 
containing  nuclei ;  5,  nuclei  of  same  cells,  seen  in  the  direction  of 
their  length  ;  6,  elastic  membrane  of  the  internal  coat,  rendered 
visible  by  the  transparency  of  the  specimen. 


PLATE  XVH. 

VEINS. LYMPHATIC  VESSELS. GLANDS    COMPOSED  OF  CLUSTERED 

FOLLICLES. 

FIG.  I.  Longitudinal  section  of  the  femoral  vein,  dried 
and  then  treated  by  dilute  acetic  acid. — 1,  Internal  coat — its 
elastic  fibres  almost  all  running  parallel  with  the  axis  of  the 
vessel ;  2,  middle  coat ;  3,  longitudinal  elastic  fibres ;  4,  trans- 
verse elastic  fibres  ;  5,  muscular  fibres  irregularly  distributed  ; 
6,  their  nuclei ;  *7,  external  coat,  made  up  of  mingled  elastic 
and  connective  fibres ;  these  latter,  in  consequence  of  the  action 
of  acetic  acid,  present  the  appearance  of  a  homogeneous  gra- 
nular mass  (8). 

FIG.  II.  Transverse  section  of  a  lymphatic  vessel  of 
the  thigh,  treated  by  dilute  acetic  acid.  Its  internal  coat  seems 
to  be  composed  of  but  a  single  layer  of  epithelial  cells. — 1, 
Middle  coat,  formed  entirely  of  muscular  fibres,  the  nuclei  of 
which  are  very  well  seen  (2) ;  3,  elastic  fibres — of  which  there 


198  EXPLANATION    OF   THE   PLATES. 

are  very  few ;  4,  external  coat,  made  up  of  connective,  elastic, 
and  muscular  fibres  ;  the  latter  (5)  run  parallel  with  the  axis  of 
the  vessel. 

FIG.  III.  A  longitudinal  section  of  the  same  lymphatic. — 
1,  Middle  coat ;  2,  muscular  fibres  seen  in  transverse  section ; 
3,  nuclei ;  4,  external  coat ;  5,  nuclei  of  muscular  fibres  encircling 
the  vessel. 

FIG.  IV.  Recent  specimen  of  a  valve  treated  by  acetic 
acid. — 1,  Nuclei  of  epithelial  cells;  2,  elastic  fibres;  3,  nuclei  of 
muscular  fibres. 

FIG.  Y.  Section  of  a  lobe  of  the  sub-lingual  gland — 
magnified  80  diameters. — 1,  Excretory  duct;  2,  its  radicles,  one 
of  which  belongs  to  each  lobule ;  3,  cavity  of  one  of  the  coecal 
pouches  of  which  the  gland  is  composed ;  4,  connective  tissue 
surrounding  its  walls. 


PLATE  XVIII. 

GLANDS    COMPOSED    OF    CLUSTERED   FOLLICLES. 

FIG.  I.  Three  co3cal  pouches  of  the  sub-lingual  gland, 
lined  by  thin  epithelium.  The  nucleus  (1)  almost  fills  each  of 
the  epithelial  cells. 

FIG.  II.  Sebaceous  follicle  from  the  scrotum. — 1,  Cavity 
of  the  follicle  filled  with  cells ;  2,  young  cells  containing  nuclei, 
and  immediately  in  contact  with  the  walls  of  the  cavity;  3, 
other  cells,  of  greater  age,  in  process  of  fatty  transformation ; 
4,  excretory  duct  filled  with  minute  globules  of  fat;  5,  con- 
nective fibres  enveloping  the  follicle  ;  6,  epidermis. 

FIG.  III.  Sebaceous  gland  from  the  external  auditory 
canal. — 1,  Body  of  the  gland  presenting  irregular  pouched  pro- 
jections (2)  ;  3,  excretory  duct. 

FIG.  IV.  Cells  from  a  sebaceous  gland  showing  different 
stages  of  fatty  infiltration. 

FIG.  V.  Epithelium  from  a  Meibomian  gland— 1, 
Young  cells ;  2,  older  cells,  filled  with  oil  globules. 


EXPLANATION  OF  THE  PLATES.        199 

FIG.  VI.  Milk  from  the  human  female. — 1,  Milk  of  the 

first  day ;  2,  colostrum  corpuscles ;  3,  free  oil  globules  ;  4,  milk 
on  the  sixteenth  day  after  delivery — from  the  same  woman. 


PLATE  XIX. 

CLUSTERED    GLANDS,    Continued. TUBULAR   GLANDS. 

FIG.  1.  Portion  of  dried  and  inflated  lung,  seen  with  a 
magnifying  power  of  25  diameters. 

FIG.  II.  Pulmonary  vesicles  from  a  fresh  lung. — 1,  Walls 
of  the  vesicles ;  2,  layer  of  epithelium  lining  the  walls  of  the 
vesicles. 

Fig.  III.  Pulmonary  epithelium  from  a  foetus  at  the  third 
month. — 1,  Cells  in  their  normal  relation  ;  2,  detached  cells. 

FIG.  IV.  A  sweat  gland,  seen  under  a  magnifying  power 
of  165  diameters  (from  the  palmar  surface  of  the  middle  finger). 
1,  Excretory  duct  lined  by  its  epithelium  ;  2,  nuclei  of  the  epi- 
thelium ;  3,  commencement  of  the  excretory  duct ;  4,  fibrous 
stroma  (connective)  of  the  gland,  showing  numerous  plasmatic 
cells  (5). 

FIG.  V.  Excretory  duct  of  the  same  gland. — 1,  Its  external 
layer  consisting  of  connecting  tissue ;  2,  its  internal  layer — 
structureless  basement  membrane ;  3,  polygonal  epithelium. 

FIG.  VI.  Same  duct  seen  in  transverse  section. — 1, 
Wall  of  the  duct;  2,  its  epithelium;  3,  its  cavity. 

FIG.  VII.  Transverse  section  of  the  excretory  duct 
of  a  ceruminous  gland. — 1,  Its  walls,  showing  plasmatic 
cells ;  2,  its  contents;  3,  young  cells,  such  as  line  the  walls  of 
the  gland ;  4,  cells  a  little  more  advanced  in  age. 


200  EXPLANATION   OF   THE   PLATES. 

PLATE  XX. 

TUBULAR    GLANDS,    Continued. KIDNEYS. 

FIG.  I.  Portion  of  the  kidney  of  a  cat— magnified  50 
diameters. — 1,  Straight  tubes  of  the  medullary  substance;  2, 
tortuous  tubes  of  the  cortical  substance ;  3,  Malpighian  tufts. 

'FiG.  II.  1  and  2,  Fresh  tubes  showing  their  internal  epithe- 
lial lining ;  3,  a  tube,  throughout  the  greater  portion  of  which 
(4)  its  external  wall  only  is  visible — contracted  and  slightly 
wrinkled ;  5,  detached  epithelial  cells ;  6,  transverse  section  of 
an  urinary  tubule ;  7,  its  epithelium  ;  8,  its  cavity. 

FIG.  III.  Portion  of  an  injected  kidney  (from  Dr. 
Boeckel),  magnified  60  diameters. — 1,  Arteries;  2,  Malpighian 
tufts ;  3,  afferent  vessel ;  4,  efferent  vessel ;  5,  vascular  plexus 
of  the  cortical  substance;  6,  same,  of  the  medullary  substance. 

FIG.  IV.  Diagrammatic  representation  of  the  structure 
of  the  kidney. — 1,  A  straight  tube  of  the  medullary  sub- 
stance ;  2,  tortuous  tube  of  the  cortical  substance ;  3,  its  ter- 
mination in  a  bulbous  expansion ;  4,  an  artery ;  5,  Malpighian 
tuft;  6,  the  efferent  vessel;  7,  capillary  plexus;  8,  veins  in 
which  the  vascular  plexus  pours  its  blood  ;  9,  relation  between 
the  vascular  portion  of  the  Malpighian  tuft,  and  the  terminal 
bulbous  expansion  of  a  tube;  10,  epithelium  covering  the  sur- 
face of  the  Malpighian  tuft,  and  lining  the  interior  of  the  uri- 
nary tube  by  the  terminal  bulb  of  which  it  is  enveloped. 


PLATE  XXI. 

^      ;  ;  /»•£;;  f.rj  j>byH&7.ifft  9t<>ill  iii.UU  ft  tfiv'Jfj.  ,*•   \\*''--' 

TUBULAR   GLANDS,    Continued. — OVAEY. 

FIG.  I.  Section  of  a  testicle  rendered  hard  by  boiling, 
magnified  50  diameters.— 1,  External  wall  of  a  secreting  tubule ; 
2,  its  internal  tunic  ;  3,  its  cavity  and  epithelium. 

FIG.  II.  A  fresh  tubule  of  the  testicle. — 1,  Outer  coat  of 
its  wall ;  2,  inner  coat ;  3,  polygonal  epithelium. 


EXPLANATION    OF   THE   PLATES.  201 

FIG.  III.  Epithelial  cells  from  the  epididymis. 

FIG.  IV.  Human  spermatozoa. — 1,  Head  of  a  spermato- 
zoon ;  2,  its  caudal  prolongation. 

FIG.  V.  Development  of  spermatozoa,  as  observed  in 
the  Guinea  pig. — 1,  Epithelial  cell  with  a  solitary  nucleus;  2, 
epithelial  cell  with  two  nuclei ;  3,  the  head  of  the  spermatozoon 
making  its  appearance  in  the  periphery  of  a  nucleus ;  4  and  5, 
two  other  cells  inclosing  a  larger  number  of  nuclei  in  the  same 
stage  of  development ;  6,  nuclei  in  which  the  caudal  prolonga- 
tion (7)  of  the  spermatozoon  is  visible ;  8,  a  nucleus  with  its 
spermatozoon  uncoiled ;  9,  free  spermatozoa. 

FIG.  VI.  Ovisac. — 1,  stroma  of  the  ovisac ;  2,  membrana 
granulosa  of  the  ovisac ;  3,  its  proligerous  disc ;  4,  zona  pellu- 
cida  of  the  ovule ;  5,  yelk ;  6,  germinal  vesicle ;  7,  germinal 
spot. 

FIG.  VII.  Ovisac  containing  two  ovules,  1  and  2. 

FIG.  VIII.  An  ovule  in  which  the  process  of  segmen- 
tation has  taken  place. — 1,  Zona  pellucida  ;  2,  segmenta- 
tion of  the  vitellus. 


PLATE  XXII. 

LIVER. SPLEEN. TPIYKOID     GLAND. 

FIG.  I.  Vena  portse  of  the  hog — magnified  50  diameters. — 

1,  A  lobule  of  the  liver;  2,  interlobular  branches  of  the  vena 
portce  /  3,  their  subdivisions ;  4,  capillary  network. 

FIG.  II.  Human  vena  portse  (from  a  child  three  years  of 
age)',  magnified  50  diameters. — 1,  Branches  of  the  vena  portce  / 

2,  their  termination  in  the  capillary  plexus. 

FIG.  III.  Intra-lobular  vein  of  the  rabbit — magnified  50 
diameters. — 1,  Boundary  of  a  lobule  ;  2,  trunk  of  the  vein  ;  3, 
capillary  network. 

FIG.  IV.   Hepatic  cells. — 1,  Large  cells;  2,  small  cells. 

FIG.  V.  Epithelial  cells  from  the  mucous  membrane  of  the 
gall-bladder. 

13 


202  EXPLANATION    OF   THE   PLATES. 

FIG.  VI.  Diagrammatic  representation  of  the  minute 
structure  of  a  lobule  of  the  liver. — 1,  Vena  portse ;  2, 
interlobular  vein ;  3,  capillary  network  (portal  plexus) ;  4, 
meshes  of  this  network  filled  with  large  hepatic  cells  ;  5,  biliary 
duct;  6,  prolongations  from  this  duct  terminating  in  blind 
extremities  ;  7,  epithelium  of  the  biliary  duct. 

FIG.  VII.  Cellular  elements  of  the  spleen. — Splenic 
cells  ;  2,  epithelial  cells  from  its  blood-vessels. 

Fig.  VIII.  Thyroid  "body  (adult). — 1,  One  of  its  cavities  ; 
2,  walls  of  the  cavity  composed  of  connective  fibres ;  3,  plas- 
matic  cells  ;  4,  epithelium  which  has  already  undergone  change. 


PLATE  XXIII. 

THE    SKIN. 

FIG.  I.  Section  of  the  skin  from  the  palmar  aspect  of  the 
last  phalanx  of  the  index  finger — magnified  60  diam. — 1,  Epi- 
dermis ;  2,  its  external  or  horny  layer  ;  3,  internal  layer,  or  rete 
mucosum  of  Malpighi.  Beneath  the  epidermis  the  true  skin,  or 
derma,  is  represented,  also  in  two  layers ;  4,  its  superficial,  5,  its 
deep  layer ;  6,  papillae  of  the  derma ;  7,  a  tactile  corpuscle ; 
8,  sweat  glands ;  9,  excretory  duct  of  sweat  glands;  10,  adi- 
pose cells. 

FIG.  II.  Section  of  the  skin  from  the  palmar  surface  of 
the  last  phalanx  of  the  middle  finger. — 1,  Cells  of  the  horny 
layer  of  epidermis  destitute  of  nuclei;  2,  polygonal  cells  of  the 
rete  mucosum:  3,  oval  cells,  which  always  form  the  deepest 
layer  of  the  epidermis  ;  4,  structureless  and  transparent  boun- 
dary line  between  epidermis  and  cutis  vera ;  5,  plasmatic  cells 
of  derma,  mingled  with  connective  and  elastic  fibres ;  6,  tactile 
corpuscle  in  the  interior  of  a  papilla ;  7,  the  nerve  fibre  with 
which  it  is  connected  ;  8,  branches  of  this  nerve  fibre;  9,  plas- 
matic nuclei  enveloped  by  amorphous  material. 

FIG.  III.  Section  of  the  skin  from  the  scrotum. — 1, 
Deep  epidermic  cells  loaded  with  pigment. 


EXPLANATION    OF   THE   PLATES.  203 

FIG.  IV.  Transverse  section  of  a  papilla  of  the  true 
skin. — 1,  True  skin  ;  2,  its  limitary  border  ;  3,  epidermis. 


PLATE  XXIV. 

NAILS   AND   HAIK. 

FIG.  I.   Transverse  section  of  a  nail  near  its  root — 

magnified  6  diam. — 1,  The  true  skin,  forming  the  matrix  of  the 
nail ;  2,  rete  mucosum  /  3,  epidermic  structure  of  the  nail ;  4, 
fold  of  true  skin  in  which  the  root  and  sides  of  the  nail  are 
received ;  5,  surface  of  this  fold  continuous  with  the  matrix ; 
6,  rete  mucosum  of  neighboring  skin,  continuous  with  that  of 
the  nail ;  7,  line  of  junction  of  the  epidermis  of  the  neighbor- 
ing integument  with  the  epidermic  layer  of  the  nail. 

FIG.  II.  The  same  section — magnified  25  diam. — 1,  Papillae 
of  true  skin  forming  matrix  of  the  nail ;  2,  rete  mucosum  of 
nail;  3,  its  epidermic  layer;  4,  line  of  junction  of  epidermis 
of  neighboring  skin  with  that  forming  the  nail ;  5,  the  only 
locality  at  which  they  are  truly  continuous :  6,  true  skin,  with 
its  papillae,  of  the  fold,  or  groove,  lodging  the  roots  and  sides 
of  the  nail ;  7,  rete  mucosum ;  8,  papillae  of  the  derma  in  trans- 
verse section  ;  9,  sweat  duct ;  10,  epidermis. 

FIG.  III.  Longitudinal  section  of  a  nail — magnified  6 
diam. — 1,  Nail ;  2,  derma  ;  3,  epidermis. 

FIG.  IV.  A  hair  from  the  scrotum  in  its  follicle,  with  a 
sebaceous  gland — magnified  50  diam. — 1,  lower  part  of  the 
shaft  of  the  hair ;  2,  its  root ;  3,  its  bulb ;  4,  epidermis  of  the  hair; 
5,  its  cortical  substance  ;  6,  its  medullary  canal ;  7,  papilla  of  the 
bulb  ;  8,  true  skin  forming  wall  of  the  hair  follicle;  9,  exterior 
epidermic  layer;  10,  interior  epidermic  layer;  11,  sebaceous 
gland;  12,  its  excretory  duct. 

FIG.  V.  Imbrication  of  the  cells  forming  the  epidermic 
layer  of  the  hair. 

FIG.  VI.  Cells  from  the  same  layer  detached  and  treated 
by  acetic  acid. 


204  EXPLANATION   OF   THE   PLATES. 

FIG.  VII.  Portion  of  the  shaft  of  a  hair.—],  Epidermis; 
2,  cortical  substance  ;  3,  medullary  canal  filled  with  cells. 


[PLATE  XXV. 

HAIES,  continued. — MUCOUS  MEMBEANE  OF  THE  ALIMENTAEY 

CANAL. 

FIG.  I.  Cortical  substance  of  a  hair  subjected  to  the 
action  of  caustic  potash.  It  is  seen  to  be  made  up  of  fusiform 
bodies,  the  result,  apparently,  of  metamorphosis  of  the  nuclei  of 
epidermic  cells. 

FIG.  II.  Hair  follicle — magnified  200  diam. — 1,  External 
layer ;  2,  internal  layer,  and  3,  amorphous  limitary  border  of 
the  involuted  portion  of  true  skin  forming  the  follicle  ;  4,  exter- 
nal epidermic  layer,  corresponding  to  the  corpus  mucosum  of 
Malpighi ;  5,  internal  epidermic  layer,  corresponding  to  the 
external  or  horny  layer  of  the  epidermis  ;  6,  bulb  ;  7,  vascular 
papilla  ;  8,  medullary  substance. 

FIG.  II.  One  of  the  papillae  circumvallatse  of  the  tongue 
— magnified  25  diam. — 1,  Section  of  the  principal  papilla  sur- 
mounted by  secondary  papillae,  2  ;  3,  epithelium,  presenting  a 
smooth  surface. 

FIG.  IV.  A  filiform  papilla — magnified  25  diam. — 1,  Body 
of  the  papilla,  surmounted  by  secondary  papillae,  2 ;  3,  epithe- 
lium presenting  also  secondary  papillae,  4. 

FIG.  V.  A  lenticular  papilla — magnified  50  diam. — 
1,  Central  orifice  leading  into  a  cul-de-sac ;  around  this  the 
capillaries  of  the  mucous  membrane  are  shown. 

FIG.  VI.  Epithelium  of  the  O3sophagus. — 1,  Two  of  its 
cells,  detached. 

FIG.  VII.  Surface  of  the  mucous  membrane  of  the 
stomach — magnified  25  diam. — 1,  Orifice  of  a  gastric  gland. 

FIG.  VIII.  Compound  pyloric  gland  of  an  infant — magni- 
fied 250  diam. — 1,  1,  Its  two  terminal  cul-de-sacs  opening  into 
a  common  outlet. 


EXPLANATION   OF  THE   PLATES.  205 


PLATE  XXVI. 

-.flOfcO  lo  SilfiV 
MUCOUS  MEHBKAUE   OF  THE  ALIMENTARY   CAXAL,   continued. 

FIG.  I.  Cul-de-sac  of  a  compound  cardiac  gland.    Its 

epithelial  cells  are  larger  than  those  of  the  simple  and  pyloric 
glands,  and  possess  a  different  shape. 

FIG.  II.  Mucous  membrane  of  the  duodenum — mag- 
nified 25  diam. — 1,  A  conical  villus ;  2,  same,  valvular  in 
shape ;  3,  a  compound  valve-shaped  villus  ;  4,  orifice  of  Lieber- 
kuhn's glands. 

.  FIG.  III.  Mucous  membrane  of  the  ileum — magnified 
25  diam. — 1,  A  villus  ;  2,  orifice  of  Lieberkuhn's  glands. 

FIG.  IV.  A  villus  covered  by  its  epithelium — magni- 
fied 250  diam. — 1,  Cells  seen  with  their  bases  presenting ;  2, 
cells  seen  obliquely ;  3,  amorphous  coating. 

FIG.  V.  Epithelium  seen  on  its  superficial  aspect — 
magnified  400  diam. 

FIG.  VI.  Cells  seen  in  tjieir  whole  length ;  their  bases 

still  covered  by  the  amorphous  investment. — 1,  A  cell  with  two 

,  . 
nuclei. 

FIG.  VII.  A  villus  deprived  of  its  epithelium. — 1,  Amor- 
phous or  slightly  fibrillated  substance ;  2,  a  vascular  loop ; 
3,  nuclei,  most  of  which  seem  to  belong  to  capillary  vessels. 

FIG.  VIII.  Villi,  injected— magnified  50  diam. 

FIG.  IX.  A  Brunner's  gland — magnified  50  diam. 

FIG.  X.  A  Lieberkuhn's  gland — magnified  125  diam. — 
1,  Its  wall;  2,  its  epithelium. 

FIG.  XI.  Orifice  of  a  Lieberkuhn's  gland — magnified  125 
diam. — 1,  Epithelium  of  the  gland  forming  a  radiating  crown 
around  the  central  open  space,  2. 

FIG.  XII.  A  solitary  gland  of  the  ileum — magnified  25 
diam. — 1,  Projection  of  the  gland;  2,  villi;  3,  orifices  of  Lie- 
berkuhn's glands. 

FIG.  XIII.  Two  solitary  ductless  glands  injected — mag- 
nified 50  diam. — 1,  Radicles  of  the  meseraic  vein;  2,  capillaries 
•urmounting  the  glands. 


206  EXPLANATION    OF   THE   PLATES. 

FIG.  XIV.  Mucous  membrane  of  the  colon,  showing 
orifices  of  Lieberkuhn's  glands. 

FIG.  XV.  Mucous  membrane  of  colon. — 1,  Lieberkuhn's 
glands ;  2,  orifice  situated  over  the  position  of  a  solitary  gland. 


SUPPLEMENTARY  PLATES. 
PLATE  XXVII. 

FIG.  I.  Ossification  in  a  medullary  canal.  —  1,  Newly 
formed  bone;  2,  oval  nuclei ;  3,  nuclei  with  radiating  processes; 
4,  line  of  junction  of  the  blastema  and  bone. 

FIG.  II.  Transverse  section  of  the  orbicularis  palpe- 
brarum  muscle. 

FIG.  III.  Meibomian  gland. — 1,  Common  excretory  duct ; 
2,  lobules.  Magnified  25  diam. 

FIG.  IV.  Kidney  of  guinea-pig. — 1,  Urinary  tubule ;  2,  its 
terminal  enlargement ;  3,  Malpighian  tuft ;  4,  aiferent  and  effe- 
rent vessels ;  5,  epithelium  covering  surface  of  the  tuft.  Mag- 
nified 240  diam. 

FIG.  V.  Transverse  section  of  an  eye-lash  at  its  base. — 
1,  Medullary  substance;  2,  cortical  substance  of  the  hair;  3, 
internal  epidermic  layer  of  the  hair  follicle  ;  4,  external  epider- 
mic layer ;  5,  internal  zone  of  the  derma  of  the  hair  follicle ; 
6,  external  zone;  7,  sebaceous  glands.  Magnified  220  diam. 

FIG.  VI.  An  internal  villus  bare  of  epithelium,  taken  from 
a  portion  of  intestine  during  the  progress  of  digestion. — 1,  Body 
of  the  villus  infiltrated  with  oil-globules ;  2,  lacteal  occupying 
the  central  axis  of  the  villus  and  ending  by  a  closed  extremity. 
Magnified  220  diam. 


EXPLANATION    OF   THE    PLATES.  207 


PLATE  XXVHI. 

THE   EYE. 

FIG.  I.  Section  of  the  two  external  tunics  of  the  eye- 
ball at  the  junction  of  the  cornea  and  sclerotica. — 1,  Sclerotica  ; 
2,  cornea;  3,  line  of  junction  of  these  two  parts;  4,  canal  of 
Sehlemm;  6,  conjunctiva;  7,  corneal  and  conjunctival  epithe- 
lium ;  8,  line  of  junction  of  conjunctiva  and  sclerotica  ;  9,  amor- 
phous layer  on  the  front  of  the  cornea;  10,  same  layer  on 
posterior  surface  of  cornea  ;  11,  iris  ;  12,  choroid  ;  13,  a  ciliary 
process.  Magnified  25  diarn. 

FIG.  II.  Cornea,  sclerotica,  and  conjunctiva. — 1,  Scle- 
rotica ;  2,  cornea ;  3,  amorphous  layer  on  front  surface  of 
cornea;  4,  junction  of  this  layer  with  the  conjunctiva;  strati- 
fied epithelium  of  the  conjunctiva  and  anterior  surface  of  cor- 
nea. Magnified  300  diam. 

FIG.  III.  Section  of  cornea  and  iris. — 1,  Cornea ;  2, 
anastomosing  plasmatic  cells ;  3,  its  posterior  amorphous  layer ; 
4,  junction  of  this  layer  with  the  sclerotica ;  5,  its  epithelial 
investment  which,  reflected  upon  the  anterior  surface  of  the 
iris,  constitutes  the  membrane  of  Demours.  Magnified  360 
diam. 

FIG.  IV.  Ciliary  muscle. — 1,  Sclerotica;  2,  canal  of 
Schlemm ;  3,  ciliary  ring ;  4,  ciliary  processes  in  which  nuclei 
of  muscular  fibres  are  seen  in  the  direction  of  their  length  at  5, 
and  in  transverse  section  at  6  ;  7,  external  circumference  of  the 
iris..  Magnified  120  diam. 


; ; 


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I'l.XVI. 


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rig.  iv: 


Fig.V. 


Kiffl 


Fiji.  I 


//«r//// (tp-l illcniin del . 


PI.  XVIII. 


Fig.  vr. 


l  illi'ii/in  del . 


Fig.II. 


C.  c  Morel  j»-ap.  -fillemin  del . 


Zitk.E.  Simon,  S 


Pl.XX. 


FU.I 


C '.Morel prcep,  HUe/iiin 


Lith.E.  Simon,  Strasbg. 


R.XXI 


('.,  Morel  pr  up,-  1 1  lie  ruin  del. 


PI.  XXII. 


Fig.  III. 


Fig.  VIII . 


C.  <Morel  pr«p^\lllcmin  dd. 


Tl.  XXIII. 


C.Jl'lorel prcep.^l'UleTrmt  del. 


LiikJZ.  Simon  aStzaskg. 


ZL.JXXIV. 


Fig.iv: 


Fl.XXV. 


• 


C.  Morel pr(tp~  Villemin.  del. 


Tl.  XXVI. 


('..  \loi-el prap.-lHle min  del 


p 


('.  Morel praff.  lillemin  del 


Lifh.E.  Sim  on,  Sir  a  si 


PI  XXVIII. 


(..  VwelpnepMUemin  del. 


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Messrs.  Bailliere  Brothers  beg  to  inform  the  Profession  that  they  keep 
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rican Publications. 

They  issue  complete  Catalogues  of  Books  on  Medicine,  Natural  His- 
tory, and  Chemistry,  which  will  be  sent  gratis  on  application. 

The  following  is  a  selection  of  works,  now  on  their  shelves,  from  the 
prices  of  which  a  Discount  will  be  made  for  Cash. 

BE  ALE  (L.)    Illustrations  of  the  Salts  of  Urine,  Urinary  Deposits,  and  Calculi.    8vo. 

London,  1858  .  .  .  .  -'.'•'"  .  .  .  .  275 

— — Use  of  the  Microscope  in  its  application  to  practical  medicine.  2d  edition,  8vo. 

London,  1853  .  . 4  25 

— — How  to  work  with  the  Microscope,  Crown  8  vo.  London,  185T  ».'"'  ''''«.'.  ^_  150 

Illustrations  to  How  to  work  with  the  Miscroscope.  Post  8vo.  London,  1859  0  50 

Tables  for  the  Microscopical  Examination  of  Urine.  8vo.  London,  185T  .  0  75 

BECOUEREL  (L-  A.)  Traite  clinique  des  Maladies  de  TUterus  et  de  ses  Annexes.  2 

vols.  8vo.  avec  Atlas  de  18  planches.  Color.  Paris,  1859  .  .  •»  ..-.-,:  ^,7  500 

BELL  (A-  NO  A  Knowledge  of  Living  Things,  with  the  Laws  of  their  Existence.  12mo. 

New  York 1  50 

BERAUD  ET  ROBIN.  Elements  de  Physiologie  de  1'Homme  et  des  Principaux  Ver- 

tebres.    2eme  edition.    2  vols.  12ino.     Paris,  1856-57         ;.7«-          .  .  .  8  00 


BERNARD  AND  HUETTE-  Illustrated  Manual  of  Operative  Surgery  and  Surgical 
Anatomy.  Edited  with  Notes  and  Additions,  by  W.  H.  VAN  BTTREN,  M.D.,  Professor 
of  Anatomy,  University  Medical  College,  and  C  E.  ISAACS,  M.D.  Complete  in  one 


volume,  8vo.  with  118  colored  plates,  half-bound  morocco,  gilt  tops.    1856.        •'"  .  •       1500 
Plain  plates     .  ,        .      ,'Vv.'        .....        '.     ,      .;,.        950 


BERNARD  (CL-)    Lecons  de  Physiologie  experimentale  appliquee  a  la  Medecine,  faites 

au  College  de  France.    2  vols.  8vo.  avec  figures.    Paris,  1855-56    .  ' .  .  3  50 

Cours  de  Medecine  du  College  de  France.    Des  effets  des  substances  toxiques  et 

medicamenteuses.    8vo.  avec  figures.    Paris,  1857        .  .  ,  .  .  1  75 

Cours  de  Medecine  du  College  de  France.    Lecons  sur  la  Physiologie  et  la  Pa- 
th ologie  du  Systeme  Nerveux.    2  vols.  8 vo.  avec  figures.     Paris,  1853         .      «  > •!«,       350 

Lecons  sur  les  Proprietes  Physiologiqnes  et  les  alterations  Pathologiques  des 


differents  liquides  de  I'Organisme.    2  vols.  8vo.  avec  figures.     Paris,  1859  .      '  •»  ; •>  <•      8  50 

Memoire  sur  le  Pancreas  et  sur  le  role  du  sue  Pancreatique  dans  les  Phenomenes 

digestifs,  particulierement  dans  la  digestion  des  matieres  grasses  neutres.    4to.  avec  9 
planches  en  partie  colorees.     Paris,  1856  .  .  .  .        ;  i  ^      .  8  00 

DAY  (G.  E.)  Chemistry  in  its  Relations  to  Physiology  and  Medicine.  8vo.  Illustrated 

by  plates,  London,  1860 5  00 

DAV  A INE  (C-)  Traite  des  Entozoaires  et  des  Maladies  Vennineuses  de  Thomme  et  des 

animaux  domestiques.  Paris,  8 vo.  1860  .  .  .  .  •  -t  •  ;\\  ~  8  00 

FAU-  The  Anatomy  of  the  External  Forms  of  Man,  for  Artists,  Painters,  and  Sculptors. 
Edited  by  R.  KNOX,  M.D.,  with  Additions.  8vo.  text,  and  28  4to.  plates.  London, 
1849.  Plain 6  00 

Colored  plates ''  ,   -•;      .         10  00 

GERBER  AND  GULLIVER.    Elements  of  the  General  and  Microscopical  Anatomy  of 

Man  and  the  Mammalia;  chiefly  after  Original  Researches.  By  PROP.  GEBER.  To 
which  is  added  an  Appendix,  comprising  Researches  on  the  Anatomy  of  the  Blood, 
Chyle,  Lymph,  Thymons  Fluid,  Tubercle,  with  Additions,  by  C.  GULLIVER,  F.R.8. 
8vo.,  and  an  Atlas  of  84  plates.  2  vols.  8vo.  cloth  boards,  1842  .  .  .  6  00 

HALL  (MARSH  ALL).  On  the  Diseases  and  Derangements  of  the  Nervous  System,  in 
their  Primary  Forms,  and  in  their  Modifications  by  Age,  Sex,  Constitution,  Hereditary 
Predisposition,  Excesses,  General  Disorder,  and  Organic  Disease.  By  MARSHALL  HALL, 
M.D.,  F.R.S.  L.  &  E.  8vo.  with  8  engraved  plates.  London,  1841  .  .  .  8  75 

— — New  Memoir  on  the  Nervous  System,  True  Spinal  Marrow,  and  its  Anatomy,  Phy- 
siology, Pathology,  and  Therapeutics.  4to.  with  5  engraved  plates.  London,  1843  .  5  00 

KOLLIKER  (A.)    A  Manual  of  Human  Microscopic  Anatomy.    8vo.  249  illustrations. 

London,  1860 7  20 

LEBERT  (H.)    Traite  d'anatomie  pathologique  generale  et  speciale,  ou  description  et 
iconographie  pathologique  des  alterations  morbides,  tant  liquides  que  solides,  observees 
dans  le  corps  humain.    2  vols.  in  folio  de  texte,  et  environ  200  planches  dessinees 
d'apres  nature,  gravees  et  la  plupart  coloriees.     Paris.  1855-1860. 
Le  tome  1,  texte  760  pages,  et  tome  1,  planches  1  a  94  sont  complets  en  20  livraisons. 
Le  tome  2  comprendra  les  livraisons  21  a  40,  avec  les  planches  95  a  200. 
36  livraisons  sont  en  vente.    Prix  de  la  livraison   .  .  .  .  .  .    8  75 

LEURET  ET  GRATIOLET.     Anatomic  comparee  du  systeme  nerveux  considere 
dans  ses  rapports  avec  Intelligence.    2  vols.  in  8vo.,  et  atlas  de  32  planches  in  folio. 
Paris,  1839-1857. 
Figures  noires  .  .  .  .  .  .  .  .  .  .  .  12  00 

Figures  coloriees          .  .  .  .  .  .  .  .  .  .  24  00 

LUDOVIC-HIRSCHFELD  ET  LEVEILLE.  Nevrologie  ou  Description  et  icono- 
graphie du  systeme  nerveux  et  des  organes  des  sens  de  Fhomme,  avec  leur  mode  de  pre- 
parations, par  M.  lo  docteur  Ludovic-Hirschfeld,  professeur  d' Anatomic  a  1'ecole  pra- 


tique  de  la  Faculte  de  Paris,  et  M.  J.  B.  Leveille,  dessinateur.    Paris,  1863.    Ouvrage 
complet.    1  beau  vol.  4to.,  compose  de  400  pages  de  texte  et  de  92  planches  4to.,  dessi- 
nees  d'apres  nature,  et  lithographiees  par  M.  Leveille. 
Prix :  figures  noires.    Half  bound   .  .  .  .          . 

figures  coloriees  ••-^••IT       •  *  '"V        .   . 

M  ANDL.  Anatomie  microsooptque,  par  le  docteur  L.  Mandl,  professeur  de  microscopic. 
Paris,  1838-1848.— Get  ouvrage  forme  deux  volumes  in-folio. 

Le  tome  I,  comprenant  I'HISTOLOGIE,  et  divise  en  deux  series:  Tiesus  et  or g ones.— 
Liqwides  organiques.  II  a  ete  publie  en  26  livraisons,  composees  chacune  de  5  fenilles 
de  texte  et  2  planches  lithographiees  in-folio  .  .  .  .  .  89  00 

Le  tome  II.,  comprenant  I'HiSTOGENESE  a  ete  publie  en  20  livraisons  .      '»"/*  >      .8000 

MANDL  ET  EHREMBERG  (C.  G.)  Traite  pratique  du  Microscope  et  de  son  emploi 
dans  1'etude  des  corps  organises,  suivi  de  recherches  sur  I'organisation  des  animaux 
infusoires.  In-8,  avec  14  pi.  Paris,  1830.  .  .  .  .  .200 

NOEGGERATHANDJACOBI.  Contributions  to  Midwifery,  and  Diseases  of  Women 
and  Children,  with  a  Report  on  the  Progress  of  Obstetrics,  and  Uterine  and  Infantile 
Pathology  in  1858.  8vo.  New  York,  1858  .  '  .  .  ,  .  .  .  2  00 

NELATON.    Elemens  de  Pathologic  Chirurgicale.    5  vols.    8vo.    Paris,  1844  to  1859    .    925 

N  YSTEN.  Dictionnaire  des  termes  de  medicine,  de  chirurgie,  de  pharmacie,  des  sciences 
accessoires  et  de  Tart  veterinaire,  ayec  le  synonomie  Latine,  Grecque,  Allemande,  An- 
glaise,  Italienne,  et  Espagnole,  suivi  d'un  vocabulaire  de  ces  diverses  langues.  1  tres 
fort  volume  de  1672  pages,  avec  582  figures.  Paris,  1858.  %  relie,  maroquin  .  .  5  50 

OTTO  (J.)  Manual  of  the  Detection  of  Poisons  by  Medico-Chemical  Analysis.  By 
J.  OTTO,  Professor  of  Chemistry  in  Brunswick,  Germany.  Edited  with  Notes  by  W. 
EIDKBHOEST.  With  illustrations.  12mo.  New  York,  185T  .  .  .  .  1  75 

OWEN.  Odontography ;  or  a  Treatise  on  the  Comparative  Anatomy  of  the  Teeth,  their 
Physiological  Relations,  Mode  of  Development,  and  Microscopic  Structure  in  Verte- 
brate Animals.  By  EICHAKD  OWEN",  F.K.S.,  Corresponding  Member  of  the  Eoyal 
Academy  of  Sciences,  Paris  and  Berlin ;  Eeade's  Lecturer  in  the  University  of  Cam- 
bridge ;  Superintendent  of  the  Natural  History  Department  in  the  British  Museum. 
In  consequence  of  the  small  number  remaining  of  the  8vo.  edition  of  this  work,  the 
publisher  has  determined  to  reduce  the  4to.  edition,  2  vols.,  India  paper,  half  Eussia, 
published  at  £10  10s.,  to 85  00 

PRICHARD.  The  Natural  History  of  Man;  comprising  Inquiries  into  the  Modifying 
Influences  of  Physical  and  Moral  Agencies  on  the  different  Tribes  of  the  Human 
Family.  By  JAMES  COWLES  PKICHAKD,  M.D.,  F.R.8.,  M.E.I.A.,  Corresponding  Member 
of  the  National  Institute,  of  the  Koyal  Academy  of  Medicine,  and  of  the  Statistical 
Society,  etc.  4th  edition,  revised  and  enlarged.  By  EDWIN  NOKBIS,  of  the  Eoyal 
Asiatic  Society,  London.  With  62  plates,  colored,  engraved  on  steel,  and  100  engrav- 
ings on  wood.  2  vols.  royal  8vo.  elegantly  bound  in  cloth.  London,  1855  .  .  10  00 

Six  Ethnographical  Maps.    Supplement  to  the  Natural  History  of  Man,  and  to 

the  Eesearches  into  the  Physical  History  of  Mankind.    Folio,  colored,  and  one  sheet 

of  letter-press,  in  cloth  boards.    2nd  edition.    London,  1850  .  .  .  .600 

QUEKETT  (J.)  A  Practical  Treatise  on  the  Use  of  the  Microscope,  including  the  Dif- 
ferent Methods  of  Preparing  and  Examining  Animal,  Vegetable,  and  Mineral  Struc- 
tures. 8vo.  3rd  edition.  London  .  .  .,#«,;,,  •  •  .  -  .  -5  00 

Lectures  on  Histology,  delivered  at  the  Royal  College  of  Surgeons  of  England. 

VoL  I.  Elementary  Tissues  of  Plants  and  Animals.    Vol.  II.  On  the  Structure  of  the 
Skeletons  of  Plants  and  Animals.    2  vols.  8vo.    Illustrated  with  340  wood-cuts.    Lond.    5  75 

Descriptive  and  Illustrated  Catalogue  of  the  Histological  Series  contained  in 

the  Museum  of  the  Eoyal  College  of  Surgeons  of  England,  prepared  for  the  Micro- 
scope.   Vol.  I.  Elementary  Tissues  of  Vegetables  and  Animals.    Vol.  II.  Structure  of 

the  Skeletons  of  Vertebrate  Animals.    2  vols.  4to.  illustrated.    London    .  .  .  17  50 

RECORDS  OF  DAILY  PRACTICE:  a  Scientific  Visiting  List  for  Physicians  and 
Surgeons.    This  little  book  is  not  intended  to  supersede  the  use  of  a  regular  visiting 
list ;  its  aim,  as  its  title  indicates,  is  to  supply  a  medium  for  taking  notes  of  the  state  of 
a  patient,  as  soon  after  the  visit  as  it  is  possible,  and  whilst  the  facts  are  still  fresh  in 
the  memory.    In  hospital  practice,  we  believe  it  will  be  found  invaluable.    Price,  in 
cloth,  50  cents,  with  tucks        .  .  .  .  .  .  .  .  .  00  75 

ROBIN  (CH.)    Du  Microscope  et  des  injections  dans  leurs  applications  a  1'anatomie  et  a 

la  pathologie.    8vo.    Parisu1849 1  75 

— * ; —    Histoire  Naturelle  dea  vegetaux  Parasites  qui  croissent  sur  Thomme  et  les  ani- 
maux vivants.    1  vol.  8vo.  et  Atlas  de  15  planches.    Paris,  1853     .  .  .  .    4  00 

SICH  EL-  Iconographie  Ophthalmologique,  ou  Description  et  figures  coloriees  des  maladies 
de  1'organe  de  la  vue,  comprenant  Tanatomie  pathologique,  la  pathologie  et  la  thera- 
peutique,  medico-chirurgicales,  par  le  docteur  J.  SICHEL,  professeur  d'ophthalmologie, 
medecin-oculiste  des  maisons  d'education  de  la  Legion  d'honneur,  etc.,  1852-1859. 
Ouvrage  complet,  2  vol.  grand  in  4to.  dont  1  volume  de  840  pages  de  texte,  et  1  volume 
de  80  planches  dessinnees  d'apres  nature,  gravees  et  coloriees  avec  le  plus  grand  soin, 
accompagnees  d'un  text  descriptif          .  .  .  .  .  .  .         44  00 

Le  text  se  compose  d'une  exposition  theorique  et  pratique  de  la  science,  dans  laquello 
viennent  se  grouper  les  observations  cliniques,  mises  en  concordance  entre  elles,  et 
dont  I'ensemble  forme  un  Traite  clinique  des  maladies  de  Vorgane  de  la  vue,  com- 
mente  et  complete  par  une  nombreuse  serie  de  figures. 

THE  LONDON  MEDICAL  REVIEW  (monthly) 360 

VOGEL  AND  DAY-  The  Pathological  Anatomy  of  the  Human  Body.  By  JULIUS  Vo- 
GEL,  M.D.,  Translated  from  the  German,  with  Additions,  by  GEORGE  E  DAY,  M.D., 
Professor  to  the  University  of  St.  Andrew's.  Illustrated  with  100  plain  and  colored 
engravings.  8vo.  London,  1847  .  .  .  .  .  .  .  .  4  50 


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